Don't understand the 'affair' thing. I can't figure out what it is that makes people think that they will not be found out. I can see how it would be fun and exciting for a little while, but the price is way, way, way too high. Even if you don't get caught, you still live with the guilt unless you are a psychopath. And you always have that hanging over your head knowing that it could suddenly pop-up for some reason at any time.
I've never known of an affair that ended in a positive way. All the ones I have witnessed were disasters. The worst case I've ever seen was a married man cheating with a married woman. Eventually they both got divorced and married each other. It was the worst marriage in history because neither one of them trusted the other one. They both were constantly calling my wife or me asking about each other. Have you seen her!? Is she there? A few minutes later another call, Have you seen him!? Do you know where he is? It was crazy. What a terrible way to live.