Getting drunk on Purim
The Rav of my shul offered the following explantion for why we get drunk on Purim. The idea of Purim is that we are supposed to see the hand of God in everything. Purim was a נס נסתר, it could easily have been explained away as coincidence etc., yet the Jews realized that it was all from Hashem. A person who has true בטחון is a happy person. he doesn't let things bother him because he knows that everything is from Hashem even what seem to be problems/difficulties. It is like the old story about the guy who is rushing to catch a plane and just misses it, he gets really upset. An hour later he hears that the plane crashed. At that point he realizes that it was for the best that he missed the plane. We are supposed to view everything in life that way. Someone who is drunk isn't bothered by anything and therefore we get drunk on Purim to reach this state (even artificially) of not being bothered by lifes problems.