I think the bad trips are good though, it's almost the point. Why are you feeling bad? It's usually because you're in a physical or mental place you don't want to be, yet, when sober, you think it is where you should be. The incongruity of the situation is the lesson and the point.

When I was in college, I tracked down some mushrooms, bought em, and ran away on my own to trip out. I found myself on a bench, next to a river surrounded by trash in a mixed industrial area. I saw cig butts and empty beer cans on the ground. Looked at my ripped jeans and thought "Am I trash? Why am I here?" It was a shitty feeling and I got really down. I realized that getting fucked up for its own sake was stupid, and it's about sharing time with others that's actually important, no matter what drug you're on. I started crying and felt horrible, but the next day, I had a new sense of worth and a new frame of reference for the world that has persisted for 20+ years. I'll always remember that shitty trip on that shitty bench.