I have never cheated on a girlfriend in my entire adult life. My father told me about his conviction when he and my mother were divorced and I believed him and thought what a great thing to be able to say.
I however was cheated on at least once, by my ex-fiancee in Brazil. I still get regular love letters from her over a year later, even got one today out of the blue... She regrets her decision and never thought she would be caught.