oh man, help?

[Joe]

Ok so my girlfriend cheated on me last week, i found out this week by one of my friends. I told her and she denied it, untill last night she admited to cheat on me while we had an argument. We broke up, and today she promices she will never do it again, and wants to come back to me. I know once a cheater always a cheater, but i really love her, how do i deal with the pain and get my life back together? help guys!