Um... keep yourself off the computer for a few days until you get over it. Okay, just kidding (although that works for me.) Otherwise, before you post, edit it over and over again until you can't find a reason why your fic would be bad; then you won't be tempted to delete it. Although that's pretty impossible. Or else, you could take my view that posting faniction on a forum is not going to get you flamed, but it will give you good advice and so help your fics be better, giving you more confidence.
(Somehow I don't think I helped at all. Excuse my rambling.)