I've only been MTBing a month. I've fallen on trails 4 times. 2 times because I was going too slow to make steep short hill and couldn't unclip. 1 time because I was going too slow over a long narrow bridge, veered off bridge, and endoed. 1 time because I hit root at top of hill and wheelied over clipped in.
Common mistake was going too slow (and afraid to go faster). I'm learning, hopefully, but confidence and skills need boost.
What mistakes have you made, or see made, often by MTBers?