Do happy people cheat?

You bring up a very good question. Have you ever watched Esther Perel's talk on affairs? If you have 20 minutes to spare, watch it. https://www.ted.com/talks/esther_perel_rethinking_infidelity_a_talk_for_anyone_who_has_ever_loved?language=en#t-1268464 "Now, all over the world, there is one word that people who have affairs always tell me. They feel alive. And they often will tell me stories of recent losses -- of a parent who died, and a friend that went too soon, and bad news at the doctor. Death and mortality often live in the shadow of an affair, because they raise these questions. Is this it? Is there more? Am I going on for another 25 years like this? Will I ever feel that thing again? And it has led me to think that perhaps these questions are the ones that propel people to cross the line, and that some affairs are an attempt to beat back deadness, in an antidote to death. And contrary to what you may think, affairs are way less about sex, and a lot more about desire: desire for attention, desire to feel special, desire to feel important. And the very structure of an affair, the fact that you can never have your lover, keeps you wanting. That in itself is a desire machine, because the incompleteness, the ambiguity, keeps you wanting that which you can't have."