I read somewhere that "Healthy attracts Healthy" and after a year with a borderline personality/ needy/controlling/manipulative guy, I had to turn the focus back on me and wonder why was I picking these guys.
They all look normal, or even better than normal at first. A "normal" or healthy person wont stay with someone with serious, untreated issues. If we stay, or keep picking them, we have to figure out why and then fix it.

When we keep picking bad apples, it really is time to start looking at ourselves.
I have found some good info in "Facing Co-dependence".