Why do I keep messing things up with nice guys?

I've been single about 9 months. In that time I've met and text varying types of guys, one I thought was lovely but turn out not, another that just fizzled out. Sometimes I just feel so sick of guys. At the same time I would love to meet someone to text and flirt with and go on a few dates and get to know. When I do meet some genuine guys (friends of friends at parties) I just mess things up though. We get on great all night but I reject them and never let them kiss me. I've regretted it then. I just dont get me...