WASHINGTON — “Does it have anything to do with us? Does it have nothing to do with us?”

In her new book, “The State of Affairs: Rethinking Infidelity” (Harper), Belgian-born couples therapist Esther Perel takes an unconventional look at infidelity. Contrary to conventional wisdom, which holds that cheating is a symptom of problems in a relationship, Perel argues that affairs can occur in happy marriages. What’s more, Perel believes, infidelity will not always destroy a relationship but sometimes give it new life.

In a recent interview with The Associated Press, Perel talked about the roots of infidelity, ways of coping with it and the secrets to maintaining erotic desire in a long-term relationship.

Associated Press: Does infidelity necessarily mean that there are problems in the marriage?

Perel: Infidelity has accompanied marriage since marriage was invented. This is part of why I wanted to write this book: it’s ubiquitous, it’s so common and it’s so poorly understood.

Of course there are the many reasons that have to do with the disenchantments and the disillusionments of marriage: resentment, loneliness, disconnectedness-disconnection, sexual frustration, sexual denial. But the more interesting finding for me, the most surprising, was that people even in satisfying relationships cheat. Infidelity occurs in good marriages, in bad marriages, in open marriages. It is not always a rejection of the partner, but more often a rejection of who we have become. It’s not so much that we are going to look for another person, but people long to reconnect with lost versions of themselves.

AP: You’ve said in your talks that love needs security, safety and reliability while sexual desire is about novelty, mystery and risk. How can we reconcile these two? Can we have both love and passion in a marriage?

Perel: Of course! There are plenty of people who love their partner and desire their partner. They are dialectical, but they are not mutually exclusive. … But that doesn’t mean that they are irreconcilable. Why people stray has multiple reasons. Oftentimes affairs take place in the shadow of mortality. I know that people talk about feeling alive when they have affairs and alive is very different from sex and excitement. Alive is what you experience when you break your own rules, when you trespass out of your own constraints, when you feel free, when you feel autonomous, when you feel like maybe for the first time in a long time you are doing something that is just for you, after you’ve been there for everybody else your whole life.

AP: So what is your advice? When infidelity does occur, what is to be done?

Perel: Some affairs break a relationship. Some affairs are basically an excuse to finally leave for both people. Some affairs remake a relationship, jolt people out of a state of complacency, realizing how far they’ve gone from each other, realizing that they don’t want to lose what they have, that they actually value it greatly. It’s a powerful alarm system. Some affairs — it’s a new love and a person wants another life. And in some affairs people realize that they actually really cherish what they have and what they want is to come back home, but they needed to have had that experience once.

AP: How should one cope with infidelity?

Perel: The first stage is dealing with the acute pain, of the shattering, of the shaking up of the foundation of the relationship, the trust, the intimacy, of the loss of the predictable future. You thought you knew your life, you thought you knew where it’s going and nothing is sure anymore. It has to do with remorse, it has to do with the acknowledgment of the hurt on the part of the person who caused it. It has to do with guilt — guilt for hurting, even if you don’t feel guilty for the affair itself. And then the second phase is finding meaning in this: What was this all about? What’s the insight? Why did this happen? What did you find there? Does it have anything to do with us? Does it have nothing to do with us? Things are not black and white.

AP: So what is the secret to sustaining desire?

Perel: Couples need to be able to revitalize themselves, to stay connected to the experiences that involve discovery, exploration, curiosity. Those create enlivening experiences. And this has nothing to do with new positions.