For some people, a one-night stand doesn't make any difference in a seven-year love affair. I don't believe the degree of betrayal is always commensurate with the egregiousness of the behavior. They are two separate things.

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.

Modern infidelity is different than traditional infidelity and sits on top of the romantic ideal that you find "the one" and that if you have everything that you need at home, you have no reason to go looking elsewhere. And if you have an affair, it's a symptom of a flawed relationship. If you don't apply the deficiency model to the relationship, then you apply it to the person. The person who strays is selfish, immature, addicted suffers from insecure attachment. And the person who doesn't stray is the committed partner: mature, stable, and non-selfish.

Many couples have never had a conversation about sexuality and sexual boundaries. The presence or lack of sex, the quality of it, the satisfaction and dissatisfaction, the unmet needs. An affair upsets the status quo by not only bringing the subject of sexuality to the forefront but every other aspect of their relationship as well. An affair yields conversation that should have happened in the beginning, but that people were afraid to have because, well, what would that mean about their relationship?

In dating, if you say no, your lover goes on to the next person. In marriage, if you say no, the person stays.

In committed sex, in marriage, people don't feel the need to seduce or to build anticipation - - that's an effort they think they no longer need to do now that they have conquered their partner. If they're in the mood, their partner should be too.

The whole notion of one person being enough for everything gets instantly challenged when you start to talk with somebody about wanting more or of wanting something else. They take it personally, feel like a failure or feel that they lack something, so you don't talk about it because you don't want to hurt, offend, or scare the other person. You also don't want to be rejected or have them leave you, whatever the reason.