Some words of wisdom please?

I did all that i could to prove my love this girl for about a year.I wasnt perfect but i was genuwine and treated her like a true lady. She treated me kind of bad through out that time(demeaning me, flirting with other guys,etc) and I have became Jaded. When we were about to break up she admiited that she treated me wrong but now claims that she has "surrendered" and will "give all her love to me".I understand she has had a history of dealing with men that were dogs and she said she did alot of it on purpose to avoid the heartache. But, after dealing with her treatment for that amount of time my attitude torwards women has changed negativly too. Among other things, I'm angry, bitter, sometimes mean, unsympathetic, and want to do less for her. I had made up mind that I would dog my next grilfriend out but we stayed together. I still love her and she has changed for the better. However, I am changing for the worse. Was she too late? Can I get back to the man I was?What should i do?