I have some experience with this, 2 suicides in my immediate family. The trick is to find the things you do like in your life and enjoy them. Screw the rest, it is not important enough to kill yourself over. Once you make that decision the rest is just clawing yourself back up into the daylight.
Depression is contagious. Stay away from deprerssed people whenever possible and when you are with them try to bring them up. It is a good exercise for everyone. This life stuff is really pretty good if you just relax and concentrate on the fun part. Laugh at the bad part, that is certainly as effective as crying about it. When you can laugh and really mean it you are cured.
