Accidentally flashed a live image (PCBSD, IIRC) onto my 1TB external HDD instead of the thumb drive. Lost years of collected music and movies that night. I learned two things:
Don’t do this sort of thing in the middle of the night, when you’re tired and should be sleeping.
Dumbest Thing you have done distro-hopping?
I just discovered something I did so idiotic I need a stronger adjective that what is in my name....