This is a repository for major, life-altering mistakes that you or others have made. Detailed accounts of specific mistakes are welcome, and so are mentions of general classes of mistakes that people often make. If similar repositories already exist (inside or outside of LW), links are greatly appreciated.
The purpose of this repository is to collect information about serious misjudgements and mistakes in order to help people avoid similar mistakes. (I am posting this repository because I'm trying to conduct a premortem on my life and figure out what catastrophic risks may screw me over in the near or far future.)
As alluded to in other comments, another interesting question is: given your past mistakes and your present circumstances, what do you expect your next "major life-altering mistake" will be?
Potential examples: continue to play football despite repeated concussions, getting together with yet another abusive boyfriend, relying on magical free will to get you through college until finally burning out and dropping out.
I'm starting a 100% commission sales job, and have had issues in the past with poor work ethic resulting in me almost failing out of school. I think I've outgrown them(this was years ago, and I've done some very hard self-motivated work since then), but if I haven't, I'm going to get hurt pretty badly by this experience.