That's just life man, welcome to the human race! I go through the same nonsense many times as well. It's pressure and stress and anxiety and all those wonderful little emotional pixies that kick us in the head from time to time.
Relax and remember that you'll be fine.
And I third the beer idea! Always works for me. :)
[FONT=Tahoma]"All I can do is be me ... whoever that is". Bob Dylan [/FONT]