What is wrong with me??

I had a job interview today and I have been a nervous wreck all day! I don't know why I was freaking out so bad. I mean geez it wasn't a big deal. All we did was introduce ourselves, talk a little about the job and the expectations and then answered a few questions. The whole interview was about 20 minutes long and it was over and done like that and yet I was freaking out ALL day! AHHH!!! Now I don't know if I can sleep tonight because I am gonna be worrying about if I will get the job or not. Man I have issues!!