My wife also asked the same “why” and “how could you” questions. I don’t know that you’ll ever get a “satisfactory answer,” because there is no answer that will make you say, “Oh, OK – I get it now.” Every situation has a different and dynamic mix of factors that contribute to the weakness which allows a cheater to suppress their conscience and silence the warning bells. The cheater essentially rationalizes away the taboos because the cheating brings a sense of power, excitement, control, or several other very powerful emotions.
In my case, yes, the guilt DID eat me alive. Although it wasn’t quite enough to make me totally break it off, it did restrain me significantly, to the point that I passed up numerous opportunities to meet the other woman. But that’s just my experience, I can’t speak for what YOUR guy was thinking.
How does a person get to the place where they can be intimate with someone else? That barrier gets broken down somehow; again, every person has their own unique mix of factors. So much of popular culture, media and pornography celebrate the pursuit of sexual pleasure, with few moral restraints. I’m sure I’ve been affected by that. Also, the other woman and I were not strangers; we lost our virginity together 35 years ago. That’s a powerful connection which contributed to the barrier getting broken down easily.
As my wife and I continue to heal after the affair, I do continually make the choice NOT to cheat. That’s pretty easy to do when you don’t have opportunity, so I guess the important thing is to make sure you stay out of situations where opportunity might arise. In my case, that means absolutely NO contact of any kind with the other woman. And, putting absolutely ALL of my energy into maintaining my relationship with my wife.