Failure. Sometimes I don't try things because I just hate that feeling when you fail at something. Suppose in a way it's good, cause I make sure I'm thoroughly prepared for whatever it is I'm attempting to succeed at and usually succeed one way or another, but I just try and avoid the feelings of disappointment and depression that come on immediately after failure. If I wasn't afraid of failing I could probably actually succeed even more, and failing in the past has ultimately never had a lasting negative effect on my life.