One of the big misconceptions is that affairs or trysts are flings about sex. And sometimes they are, but much more often they are about desire. And that is very different. The desire to feel special, to feel seen, to feel appreciated, to be laughed at or with. The desire to be desired. That does not manifest in a sexual act per se. Affairs make you feel alive. Alchemy means it's not about the actual sex, but the sexuality, the energy, the aura. It's the imagination and anticipation of it as much or instead of the actual experience of it.

If a woman isn't feeling sexual with herself, she won't respond to advances from any partner, male or female. When this woman goes dancing, she's finding a connection with her own erotic self. It might be about being on a dance floor, feeling free, not having to feel at all responsible for anybody else's well-being. For other people, it might be about going on a hike for four days by herself and reconnecting with nature and strength and endurance and beauty.

There's something very full in knowing that your partner accepts you as is.

You know what happens to sex in marriage? Instead of inviting desire, you monitor it. Especially men: You let her sleep late, you take the kids to the park, and all that time you're thinking, "Tonight I'll get some." That doesn't work.

At this point, we are living one of the greatest experiments in humankind - to create something that has, throughout history, been considered a contradiction in terms - a passionate marriage. Passion has always existed, but it took place somewhere else. Everything that we wanted from a traditional marriage - companionship, family, children, economic support, a best friend, a passionate lover, a trusted confidante, an intellectual equal - we are asking from one person what an entire village once provided. And couples are crumbling under the weight of so much expectation.

In desire, there must be some small amount of tension. And that tension comes with the unknown, the unpredictable. You can close yourself off at home and say, "Whew, at last I'm in a place where I don't have to worry," or you can keep yourself open to the mystery and elusiveness of your partner.

To look at infidelity from the point of view of sex is a complete narrowing of the phenomenon. There's a reason that the commandment is repeated twice in the Bible - once for doing it and once for thinking about it. We have always created structures and broken structures. It is essential to the human spirit.