For the last GF, the existence of the relationship to begin with is on her. The end of it was definitely on me.
I started seeing the GF on a friends with benefits level. Then she started asking me to 'escort' her to various functions related to her work, like charity balls and cocktail parties. I was sort of transitioning jobs at the time and was a little tight on money and was about to move in with my parents. She invited me to come live with her at her apartment (provided to her as a benefit from her job), and I went along with it. It was really just a financial arrangement for me and for her she got sex and a reliable, nice-looking fellow on her arm at all of these stupid functions.
Then she started getting into a lot of drama. Yelling at the doorman because she thought he was smirking, blowing up at the cleaning lady for knocking over something, picking a fight with an old lady at the market over a box of raisins. She never flamed at me because she knew I wouldn't stand for it a second, but it seemed that every where we went she would stir up some sort of chaos.
Then she started taking these long business trips. Like 4 weeks at a time, etc. So I slept with another woman when I was up in Boston at a conference. I told the GF about it, and she said it was fine since she had been away but warned me not to do it again. Of course I did it again, with two other girls, several times in the GF's apartment.
When she came back from another long trip, I picked her up at the airport and brought her back to the apartment. I was planning on telling her I'd been with other people and just ending the relationship. We had just gotten in the elevator in the lobby of the building and one doorman whispered to the other, "The brunette he had over last week was much hotter." The GF has bat-like hearing, and she caught this just as the door closed. She glared at me the whole ride up to the 51st floor, then as soon as we got in the door she insisted on having sex. I tried to tell her but she kept shooshing me and saying, "After, after."
I tried to find the right time to introduce the topic over the next few days but she just wanted sex every time I tried to bring it up. A few days later she was heading out of town again for a very extended trip, and she finally confronted me about the comment on the drive to the airport. She was very cool about it, she asked me outright what that comment was about, what I had so persistently been trying to talk to her about, and I told her bluntly what had happened. She said okay and sat icy cold until we got to JFK. She got out, got her bags, didn't say goodbye, nothing.
A few days later, just after Christmas, I got an email from her. It said, "I'll be back on February 12. I'll take a taxi back to the apartment. Don't be there." Fine by me.
