one time while trying to remove the "glaze" from a set of front brake pads, I got out on an empty highway and got it up to 60 mph then slammed the brakes almost hard enough to lock em up.
j/k shark, actually, worse mistake I ever made was not trusting my instincts. had a cavalier start running real bad over the course of a couple of days. finally it wouldnt start at all. my first thought was plugged cat. converter (especially cause it had been making rattling noises). spend 2 weeks and too much $$ checking and changing all sorts of things like fuel injector, fuel pump, timing belt, etc. turned out to be the cat after all.
ouch.