I am so sorry, rtb. I have been there. This is not on you. You are not lacking in some way. As Divine so rightly said, cheaters cheat. Once a cheater, always a cheater. It is just a fact. Nothing you could ever do would ever, ever have been enough to keep him from cheating, because that is who he is. This is not on you. Try to work on not judging yourself so negatively and opening to the possibility that he was not the person you have constructed him to be. He is someone else. That, itself, is painfu, BUT, in the long run, it does offer solace and help to healing knowing that your brains's idealized image of him is kind of, well, totally inaccurate, as it sadly turns out. Remember, you aree hardly the first person this has happened to. Happens all teh damn time. Cheaters cheat. It is what they do. They like it. It is fun for them. They especially enjoy successfully deceiving their spouse--it is a rush to lie and get away with it. They like the danger. It is a high.

So, be sad, but really work on the part about judging you. That is a big key here.

He will almost certainly cheat on her when he gets bored again or runs into some other hotter, younger, more dangerous person. Not to worry. You just won the lottery, you just can;t see that yet. But you will. I promise you will.

Sending love and kindness to self.