What was your biggest mistake either in training (indoor or out), a race, recovery, or social ride? Did you enter a crit after eating a hot dog? Wear briefs under your shorts? Brag about how fast you are only to find out you had Km set instead of miles? Draft behind a strange car and crash into it because they hit the brakes not knowing you were there? Sprint for the finish only to hear the “one to go” bell? Bring it.
I’ll start. For the record I’ve made every mistake in the book twice. But this one is amateur all the way…I crashed myself out at the very end of a group ride because I stuck my front tire in an expansion crack of a concrete road (underpass) staring at a women’s butt. Wouldn’t have been a big deal if I was the only one to go down but, I caused a buddy to crash as well. As if that wasn’t bad enough we caused a bit of a backup with cars because the intersection was one used to get on and off one of the freeway loops here in Phoenix, AZ. Quite the 
move!