I was reading them recently and they had a terrific interview with Ira Glass, and he said something so interesting, that I really believe, about infidelity:
“For example, before people begin an affair, before they cheat, the real transition begins when they confide in someone else. That’s where the betrayal begins…And as soon as he starts having truths that he doesn’t tell to her but that he tells to someone else…that’s the beginning of the end for them.”
I see this all the time in the stories people tell me. When you are confiding more to your friends than to your lover/spouse, if you are being more intimate with others than with them, that’s when trouble starts. It’s not that you can’t be intimate with other people, it’s just that you can’t have stories you withhold from your lover but share with others, especially others you find attractive; that is a tiny crack between the two of you, which can easily grow if you put enough pressure on it.