I have this too. It is based on experience. There is something about me... perhaps my look or something that only attracts people who are "bad". Either they just want sex and nothing else or they want to make me think they are interested in me and then pull the rug out from under me. I have had people state that I am just not being open to the good people but that is just not true. The good people are there but they aren't interested in me or, my entire persona is such that I actively send them running because I react badly, to any kind things they try to do with me.