Are You Fun?
How do you choose your friends? Who do you choose to be around? Most likely these people are ones you perceive to be "fun".
Women are the same as us in this regard. They want a man that's fun to be around and they have a good time around.
I think about the time I was getting laid the most. I was a wild man in those days, always having a good time around women, partying it up every second I had, being the life of the party.
Consider the idiot who tears it up on the dance floor and can't dance worth a damn. This guy usually has women surrounding him. Why is this? Because he's fun! The guy knows how to have a good time and this is attractive to women.
Now, I realize you can cite many examples where the woman is with a total jerk who you wouldn't consider "fun" at all. But in some odd way she probably thinks he's really fun to be around.
I am reminded of my past relationships also, wherein if I got too serious with the girl, things would soon end.
When the fun ends, the girl goes in my experience.