I've never had a girlfriend. :-(
The closest I had to one was a total *****. This is EXACTLY how we got along (she's John Cleese in this video).
Everything I would say she would contradict. There were some positives to her, but what finally broke the camel's back was when she told me that she couldn't be faithful because, "If someone I was dating was happy when I wasn't, I would just cheat so that he could still be happy." I then spent probably ten minutes telling her that how she was wrong and, even though she agreed, she didn't care. Even though we weren't dating or anything and we were only friends, I only talked to her one other time ... Earth Day, to be exact (just because she's big into that and, since it fell on Good Friday, nobody would be celebrating Earth Day in particular except her so I wanted to be a little supportive). Since then I have not talked to her. I was, and still am, so pissed at that kind of insolent attitude that if I never see her again for 10,000,000 years it would be WAY to soon.
Now, there was another girl whom I knew that I had the hots for, and I'm positive she felt the same way for me. God, did she turn me on! In retrospect, I should have tried for some sex (and the way she turned me on, there would have been nothing "casual" about that casual sex! ;-] ), but in my anger of circumstances that had happened, I washed my hands of everything we had done. I haven't heard a word about her since early 2010.
I don't regret it, but if I somehow woke up back in mid 2009 when we met, I would have tried for that eventual outcome.