How to forget something that is not pleasant?!

How to forget something that is not pleasant?

Last weekend I went out with a group of friends (let's say acquaintances), they were not really nice, I didn't enjoy the night and they made me put $ 30 to buy wine or other stuff that I really did not want. Now I realize that I shouldn't have gone out with them, I just went because there was one girl that I knew and I had nothing else to do at home. Now, I regret to have spent those $ 30 in something I didn't really enjoyed. I feel guilty now because I contantly restrain myself from spending money in things that I like just to save for school. Now those damned $ 30 are hammering my head. What do you think I should do to block those strange feelings of stupidity and fault? What can I do to feel better? How can I forgive myself and feel normal again?
This is very weird I think I need a shrink. Has anyone been in the same situation as me. I cannot talk to my family because I feel guilty for not spending my money for good reasons and not even enjoying it.

THANKS!!!

Everyone does things that they regret. All you can do is learn from it. You probably won't get your $30 back, sad to say. In the future, you should avoid hanging out with these people, and don't give in to pressure to spend your money again.