Hmm, let's see:
1.) Picking a crappy major because it was an easy exit out of college. I've yet to benefit from this major other than to tell jobs that I do have a bachelors degree, which is the bare minimum for most salaried positions around here.
2.) Not having more sex in high school and college, despite numerous displays of interest exhibited by a few girls. I was severely underweight and it affected by self-esteem and self-confidence to the point that I didn't think anyone could possibly like me outside of my few friends.
3.) Suffering from trust-issues due to the reason above and because of my parents' divorce. Pushed everyone away, even those that had sincere interest in getting to know me better.
4.) A lawyer from a prestigious firm in Washington D.C. offered me a job while I was attending a trial for a class project. I told her I already had a job at Best Buy, and she walked away.
5.) Squadered 4 years in the military on an MOS (0311) that amounted to dog shit in the real world.
6.) Not being there for my little brother, and being a better role model after our father left us. Now he's a full-blown alcoholic, drifting in the wind somewhere, living hand to mouth and has distanced himself from everyone.