After nearly five decades of listening to couples in crisis, renowned psychotherapist Esther Perel says the reason people cheat isn’t always what we assume. It’s not just about lust, or boredom, or one too many margaritas. According to her, it’s about something far more unsettling and sad: a sense of “deadness” in the relationship.

In an interview with The Telegraph, Perel explained that after 45 years as a sex therapist, she’s come to believe that affairs are often a response to feeling disconnected from your own vitality. “Sometimes [the reasons] have to do with the relationship — rejection, betrayal, disconnection, or alienation. Loneliness is a big one,” she said. “Other times, the reasons are internal and have little to do with the relationship itself.”

Still, the biggest through-line she’s seen is this slow, creeping “deadness,” where intimacy morphs into routine, and passion suffocates under domestic familiarity. That’s when partners may start to drift—not necessarily because they’ve fallen out of love, but because they’ve stopped feeling alive.

Sex Therapist of 45 Years Reveals the Real Reason People Cheat

To counter this, Perel emphasizes the idea of “aliveness,” which she links to curiosity and what she calls “differentiation.” That means rediscovering your partner as if you don’t know everything about them. “It’s about opening yourself up to the possibility that you don’t know your partner as well as you think,” she said. 

Instead of falling into the daily grind—school pickups, grocery lists, repeat Netflix binges—Perel urges couples to carve out space for play and unpredictability. “Play is essential,” she said. That could mean sharing weird stories, trying a new recipe, starting a ritual, or simply doing something unfamiliar together. The point is to see each other differently.

She believes that sustaining long-term relationships also means giving up the fantasy that your partner will one day become your mirror image. “You can’t make someone be exactly like you,” she said. “You accept your differences and understand that someone can do something for you that means nothing to them, and you can do things for your partner even if you’re not interested yourself.”

So why do people cheat? Often, it’s not because they’re looking for someone else—it’s because they’re looking for themselves. And that search, Perel says, starts not with fixing your partner, but with reawakening your own sense of desire and surprise.