Starting university with chemistry rather than computer science. Started on chemistry because I'd really enjoyed it at school, because my teacher was fantastic; realised I didn't actually like it at all. If I'd started on comp sci (and this was in 1985), I'd have done well, I'd have had much more money earlier, and my ridiculously intensive personal hobbies wouldn't have been affected.
tl;dr unexpectedly hazardous: good teachers.
Was that outcome predictable in advance?
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.)