Sometimes it's not that easy.
I spent 8 years in the relationship from Hell. I tried breaking up on at least 9 occasions, none of which worked. I wanted out, and in the worst way. Fights, being commanded, tears upon tears, bushels of flowers (I asked FTD once if there was an 'Im sorry' bouquet...and there is...). thousands of hours on the phone all night, it was getting to me. Yeah, now it's easy to say get a restraining order, but if you have someone who can play you emotionally, then you get pretty frustrated.
I spent a year and a half getting her to go to New York to get her out of the way, then found someone else.
If there is a Hell, I'll probably burn for this alone. It has been the worst betrayal to someone in my life. I do (and should) feel like s$%t about it 10 years later.
I'm not taking his place for a second, but I will let you know (and I don't have an explanation for it), in that once you have a girlfriend, there is a certain type of woman who finds that attractive (not the one you're dating, either). Probably the increase in self-confidence does it, I don't know. It's an equal-opportunity betrayal system.
But men being what they are, in a world without rules, we'd all be unfaithful to an extent. Or not. Some bad guys can fake being 'nice', some have this thrust upon them.
But as the Russians say; trust, but verify.