Even a good marriage leaves people with longings for certain things their marriage will never be. So, do they accept that, make compromises, and say, "You can't have everything in life," which is what we always did? Or do they say, "I deserve more. I want to experience that thing and, you know, I have fifty more years to live than I used to." It's not necessarily that we have more desires today, but we do feel more entitled to pursue them. We live in this "right to happiness" culture, and yes, we do live half a century longer than we used to.

On some level we trade passion for security, that's trading one illusion for another. It's a matter of degree. We can't live in constant fear, but we can't live without any. The fear of loss is essential to love.

We know desire is rooted in absence and yearning. What you don't have is often ten times richer than what you actually experience. An affair is a perfect erotic plot because it fits the erotic equation of psychotherapist Jack Morin: "Attraction plus obstacle equals excitement.".

People cheat on each other in a hundred different ways: indifference, emotional neglect, contempt, lack of respect, years of refusal of intimacy. Cheating doesn't begin to describe the ways that people let each other down.

The vast majority of unfaithful people are experiencing a conflict between their values and their behavior, and that is the mess of infidelity. It's not an either-or. The idea that you would ask, "How can you say you love your husband and you want to stay married, and you also are having an affair?" Because we are not the same woman, or the same man. Because sexual revolutions don't take place at home. Because for most of us, freedom wasn't something that we experienced in our family, but usually outside of our family.

There is no sex without a cue. People who date have their cues at home, before they meet. You think about where to go, what to eat, what to do and say. Sometimes the cue is short - - just before we reach the bar - - but sex is never just spontaneous. Spontaneity is a myth.

I believe that the vast majority of people that are unfaithful are monogamous in their beliefs. The ones who are not monogamous in their beliefs either live in poly relationships or consensual non-monogamous relationships, or they have divorced. If it's very bad, then people don't stay married these days in the West. They can be married and have their family, but they want something else - they want something that they don't have in their lives, or simply to be someone that isn't who they are in the context of their marriage.