The whole negative-attitude thing referred to earlier is easy to criticize, but a whole different thing to break, esp. after years of rejection.
If a negative attitude persists, it may mean you're hanging out with the wrong people anyway.
My own finding (though things didn't work out in the long run) is that if you find the right person (probably by hanging out in the right crowd), the negative attitude corrects itself somewhat.
Join common-interest groups and clubs. I don't know of other solutions. Bars and people at work never worked out for me.