When I got divorced in 1994, my ex and I still saw each other occasionally. There were never any hard feelings. We just simply grew apart as a married couple. We were easily able to put the cheating behind us because we both knew why it happened. However, nine years after our divorce, I got a call from one of her creditors asking for my help in paying one of her bills that started out as being in both of our names. I explained to them that we are divorced and the bill is only in her name now. So after not having contact with my ex for about seven years, I called her and told her that someone would probably be bugging her soon if they have not already. Then I proceeded to try to give her a lesson in finances, and she actually listened this time.
A relationship between a man and a woman isn't that different than a regular friendship between two dudes. You share a common interest. that cynicism wasn't present when you were a kid, playing with little girls in school. It's a learned trait.