I really need some perspectives!!

About 12 years ago I was in a relationship with a great girl. I had a good education and career. She had an affair with a part time bartender. At the time she was 24 and I chalked it up to immaturity. We stayed together but after about a year and a half split up and she admitted she had seen him behind my back at times. So I was done. In 3 weeks she was back at my door begging to come back. (A lot of weird things happened but over the course of 7 months we got back together so I'll spare the details). We had a really good relationship but intimacy...not so much. And then I cheated. She found the old bartender guy on facebook and started seeing him and moved off with him. She once told me her lesson back then was that he was not someone she would want even if she and I didn't work out. I just couldn't imagine going back to an ex I had so much drama with and actually ran away from. All I know is I feel incredibly guilty about my affair and I deeply miss our relationship and am having trouble moving on. I know this is a crazy story but I am just in shock.

Twenty-four? Immaturity? Or is the truth that we should chalk it up to you not wanting to vote with your feet, for whatever reasons? No, don't spare the details, thanks all the same. Tell me WHY you took her back despite she'd shown she didn't value being in a relationship or being in one with you (and/or). This, I reckon, holds the key to why you're having trouble moving on.