I think every 30 day challenge blogger I've read has had trouble with this prompt. It's an odd question because I think most people don't remember individual rides for too long after they happen.
The only one that's coming to mind is the first serious fall I ever had. I'm being called away to tire out a still-constantly-meowing kitten, though, so I'll just link you to where I told the story.
Is that cheating? Whatever.