Sometimes we can get addicted to the drama. Human's also don't like to feel rejected so you naturally want to win him back. He's obviously playing both of you. You could also have co-dependent issues.

The best way to get over this urge to let him come back is, to cut off all contact, even emails/Facebook. You need to get him out of your system like a bad drug. Remember you deserve better than what he's offering. He'll tell you both what you want to hear - don't believe it.