What do you do, when someone is being so cruel? Not sticking to promises, meeting and flirting with people behind your back, sending inappropriate emails to people they really shouldn't, saying things they really shouldn't? Upsetting you on purpose and seeming to relish in it, even though they deny all knowledge of doing it?
What do you do, when your mother gave your father one, ten, one hundred chances, always took him back, always hoped 'this time would be different', what do you do when your actions mirror hers, and you can't seem to break the cycle? When you don't have the energy you need to say 'Stop! I will not let you do this to me?'
What do you do when you look back on old photos and old memories and wonder how, why, when it all got so wrong? Why is he saying these hurtful things? Why won't you make it stop? Why can't I make it stop?
How did we get so mean?

you know what you must do. You recognise the pattern as well. You have to love yourself and know your own worth. If he can't be a man, then you should finish with him, and find yourself a real man.
he is mean because he is not yet mature enough to handle a real relationship.