I've never been cheated on -- at least not that I know of.
Maybe it's because I wouldn't ever put up with being cheated on. There wouldn't be any "understanding", there wouldn't be any "talking about our problems". There'd be suitcases on the front lawn.
There's a great line in the movie "The Tall Guy". Jeff Goldblum cheats on Emma Thompson. When she finds out, he starts trying to explain himself, and she shuts him up with: "When you were having sex with her, how much respect did you have for me?"