Why Good People Cheat (And It's Not About You)

"How could he do that?" "Why did she look elsewhere when everything was going well?" "Wasn't I enough?"

I hear these questions every week in my practice. They are natural, legitimate, and often the first to emerge after discovering infidelity. But they're based on a premise worth examining: the idea that infidelity would be a verdict on the quality of the relationship or the worth of the person who was cheated on.

The reality is more complex. Infidelity is almost never an accident, but it's not simply a matter of physical desire or lack of love either. Behind every act of cheating lies a deep psychological motivation—one that the unfaithful person themselves often doesn't fully understand.

I'm Gildas Garrec, a CBT Psychotherapist specializing in CBT therapy in Nantes, and I work with individuals and couples facing infidelity. This article is not intended to justify cheating or to absolve anyone of responsibility.

Rather, it aims to shed light on the psychological mechanisms at play—because understanding the "why" is often the first step toward moving forward, whether you're the person who was betrayed or the person who cheated.

What Science Tells Us About Infidelity

Before diving into the 6 reasons, let me establish some key facts. According to an IFOP 2025 survey on French sexuality, 46% of men and 32% of women report having been unfaithful at some point in their lives.

These figures, stable for several years, remind us that infidelity is not a marginal phenomenon—it's a recurring human reality, present in all cultures and throughout history.

Neuroscientist Helen Fisher, whose work on the biology of love is widely referenced, has identified three distinct brain systems linked to romantic life: sexual desire (testosterone/estrogen), romantic love (dopamine), and attachment (oxytocin/vasopressin).

These three systems are not always aligned. You can be deeply attached to your partner while experiencing intense desire for someone else. This isn't an excuse—it's a neurobiological fact.

Esther Perel, a couples psychotherapist and author of The State of Affairs, summarized it this way: "Infidelity doesn't always mean something is wrong in the relationship. Sometimes it reveals that something is wrong in the person."

It's this individual dimension that we're going to explore.

The 6 Psychological Reasons for Infidelity

1. The Need for Narcissistic Validation

This is probably the most frequent motivation, and the most difficult to admit. The person isn't necessarily looking for a better relationship or a better partner. What they're seeking is confirmation that they are still desirable, seductive, important.

Within an established couple, compliments become rare. Routine sets in. The other person's gaze, once admiring and enthusiastic, becomes familiar. For some people whose self-esteem largely depends on external validation, this normalization feels like implicit rejection.

The extramarital encounter then offers a flattering mirror: "You're fascinating," "I've never met anyone like you." In CBT, we identify a schema of approval-dependence here: personal worth is conditioned on others' opinions, and one person's attention is no longer enough.

What this reveals: a narcissistic fragility that existed before the relationship and was not created by it.

2. Avoidance of True Intimacy

This may sound paradoxical: how could an intimate relationship with a third party be a way to avoid intimacy? Because true intimacy—the kind that requires showing yourself as vulnerable, imperfect, dependent—is terrifying for some people.

An extramarital relationship, by nature, is compartmentalized. You don't share bills, arguments about parenting, or anxieties at 3 a.m. You share the lightest, most seductive version of yourself. It's intimacy without the risks of true intimacy.

People who have an avoidant attachment style are particularly vulnerable to this mechanism. Infidelity allows them to maintain emotional distance from their primary partner while satisfying their need for human connection—but in a controlled dose.

What this reveals: a fear of vulnerability and emotional dependence, often rooted in childhood.

3. Addiction to Novelty and the Dopamine Rush

Helen Fisher demonstrated in her neuroimaging work that the beginning of a romantic relationship activates the reward circuit of the brain in a way almost identical to cocaine. Dopamine, norepinephrine, serotonin: the neurochemical cocktail of nascent passion is powerful, intoxicating, and—here's the problem—temporary.

After 18 to 36 months on average, this cocktail fades. Romantic love evolves into attachment, calmer and more stable, but also less electrifying. For some people, this transition feels like a loss. Even a happy marriage becomes routine and fails to produce the same rush.

Infidelity then offers a neurochemical reset: the secrecy, the novelty, the forbidden element amplify the dopamine surge even more. Some people develop a genuine addiction to this intensity, moving from one affair to another not from lack of love, but from inability to tolerate calm.

In CBT, we speak of sensation-seeking and low tolerance for boredom. These schemas are often correlated with impulsivity traits and, in some cases, narcissistic or borderline personality disorders.

What this reveals: difficulty distinguishing excitement from love, and investing in depth rather than intensity.

4. Unconscious Revenge

"You hurt me, so I hurt you." This motivation is rarely stated so plainly, but it's clearly present in a significant number of infidelity cases.

It may be revenge following a previous infidelity by the partner, but also more diffuse revenge: against chronic inattention, repeated humiliation, a power imbalance in the relationship.

The person isn't so much seeking pleasure as seeking symbolic reparation for a wound. "If I don't matter to you, I'll matter to someone else." It's an act of communication—clumsy, destructive, but communication nonetheless.

In CBT, we identify injustice schemas and accumulated frustration here. The person lacks the tools to express their suffering directly (assertiveness) and resorts to indirect behavior whose consequences far exceed the initial intent.

What this reveals: unresolved conflicts in the relationship, a communication deficit, and sometimes a history of unprocessed wounds. If you recognize this dynamic, work in couples therapy can help dismantle this mechanism before it causes irreparable damage.

5. The Identity Crisis

Forty arrives. Children grow up. The career stalls or, conversely, peaks. And suddenly, a question emerges: "Is this life really mine? Did I choose all of this, or did I just go along with it?"

A midlife crisis—or any major identity crisis—is fertile ground for infidelity. Not because the person no longer loves their partner, but because they no longer recognize themselves.

The extramarital affair then becomes an act of reinvention: "With this person, I'm someone else. Someone freer, younger, more alive."

Esther Perel observes that in these cases, "the person isn't looking for another partner. They're looking for another version of themselves."

This dynamic is particularly painful for the betrayed person because it gives the impression that the entire life built together is being called into question. Yet it's often not the relationship that's at issue—it's the person's relationship with themselves.

What this reveals: a need for identity exploration that could have, ideally, been expressed and addressed within the relationship rather than in secret.

6. Compensation for Émotional Deficiency

This is the reason most "understandable" in many people's eyes, but it deserves nuanced examination. Yes, some people cheat because they suffer from an emotional, sexual, or affectional deficit in their relationship. The absence of tenderness, desire, deep conversations, complicity—these gaps are real and painful.

However, CBT teaches us to distinguish actual deficiency from perceived deficiency. Some people have such high emotional expectations that no partner can meet them.

Others interpret the slightest decrease in affection as abandonment. And still others have never communicated their needs to their partner, assuming that "if they really loved me, they would know."

Infidelity motivated by emotional deficiency is often an alarm signal—not that the relationship is doomed, but that an essential conversation never happened.

What this reveals: an imbalance in the couple's emotional needs that deserved to be named and worked through, ideally before the infidelity occurred.

Physical, Émotional, and Digital Infidelity: The Boundaries Are Shifting

It's important to note that these 6 motivations don't apply only to physical infidelity. Émotional infidelity—sharing a deep intimacy with someone outside the relationship—and digital infidelity—sexting, exchanges on apps, online flirting—often respond to the same psychological mechanisms.

The IFOP 2025 surveys actually show that 28% of people in relationships consider sexting a form of infidelity, while 34% judge intimate emotional conversations with a third party to be more serious than a purely physical affair.

What Infidelity Does NOT Say

Understanding the motivations behind infidelity also means knowing what it doesn't signify:

• It doesn't mean the betrayed person is insufficient. Infidelity says more about the person who cheated than the person who was cheated on.
• It doesn't mean love has disappeared. Many unfaithful people genuinely love their partner. It's disconcerting, but it's a clinical fact.
• It doesn't mean the relationship is doomed. 63% of couples stay together after infidelity, and a significant portion emerges stronger—provided they do deep work.
• It doesn't mean the unfaithful person is "bad." They are human, fallible, and often in pain themselves. This observation doesn't erase responsibility, but it helps us move beyond the simplistic victim/perpetrator framework.

How to Move Forward: The CBT Approach

Whether you're the person who was cheated on or the person who cheated, CBT offers a structured framework for working through the roots of infidelity:

If you've been betrayed:

– Understand that the trauma of betrayal is a genuine psychological shock that deserves professional support

– Learn to rebuild trust if you choose to stay, or to navigate the grief of lost love if you choose to leave

– Work through intrusive thoughts and ruminations that follow the discovery

If you've cheated:

– Identify the real motivation among the 6 described in this article

– Understand the underlying cognitive schemas (need for validation, avoidance, impulsivity)

– Develop alternative behavioral strategies to meet the initial need without resorting to infidelity

In both cases:

– Individual work is often necessary before or alongside couples work

– Honest communication—however painful—is the only path to reconstruction

When to Seek Professional Help

If you're going through an infidelity situation, whether you're in doubt, pain, or guilt, professional support can help you see clearly. Not to judge, but to understand. Not to choose for you, but to give you the tools for your own décision.

I see clients at my office in Nantes and offer online sessions for both individual and couples sessions. The first step is often the hardest: daring to talk about it.

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Also Worth Reading:

– Infidelity: The Complete Guide to Understanding and Taking Action — The foundational article on infidelity

– Overcoming Infidelity as a Couple: The 5 Steps — The concrete protocol for rebuilding

– The Trauma of Betrayal — When infidelity triggers PTSD

– Digital Infidelity: When Your Phone Destroys Your Relationship — Cheating in the digital age

– Can You Forgive Infidelity? — The conditions for true forgiveness

– Social Media and Your Relationship — Protecting your relationship from digital influence

– Breaking Free from a Toxic Relationship — When repeated infidelity is a sign of toxicity

Also Read

• Infidelity in Relationships: Understanding, Overcoming and Rebuilding (CBT Guide 2026)
• Digital Infidelity: When Your Phone Destroys Your Relationship
• Can You Forgive Infidelity? The 3 Conditions for True Forgiveness
• Do I Need a Therapist? 10 Telltale Signs

Do you recognize yourself in this article?

Take our Couples Communication Test in 30 questions. 100% anonymous – Personalized PDF report for €9.90.

Take the Test → Also Discover: Attachment Style (35 questions) – Personalized report for €14.90. Want to go further? As a CBT Psychotherapist in Nantes, I offer structured and compassionate support. Contact me to schedule your first session.

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Watch: Go Further

To deepen the concepts discussed in this article, we recommend this video:

Rethinking Infidelity - Esther Perel | TEDTED