I don't understand some of the things I do

I hate how I don't like most people before I meet them
I'll say "I hate so and so" and then I meet them, and they're great people.
I think I just do it so if I find out they don't like me, I won't be as disappointed. Because I can just say "Oh well, I didn't like them anyway."

It's actually a terrible habit

There's probably so many people that I could be really good friends with right now that I don't even know of because I let them slip right by me by saying 'I don't like them' It's kind of weird to think about