@mrfriendly8181
Main Character (preferably male) fucks up and has to move on and build a new life.
And most likely he would fuck up his new life.
From what I've seen in the relationships around me, male cheaters fall into two categories.
Men suffering from lack-o-nookie at home.
Men who have rejected the notion of monogamy. These men may pay lip-service to monogamy and even marry a woman, but they don't mean it.
In the former case, He's not the one who fucked up the old relationship.
In the latter case, those men will never stop cheating. Even if he rebuilds his life and finds a new wife, he will cheat on her.