The first time was youthful bravery–I was playing hockey with people far better than I (not older, merely better) and they slammed me into the boards. That's something almost heroic, at least when you're twelve.
No, the second time was two days ago. I finished a delightful breakfast with a friend and as I walked out of the restaurant, I focused on the door to the street and the weather outside–and completely ignored the interior plate glass door, slamming right into it at full speed.
The important lesson: while it matters a lot that you have a goal, a vision and an arc to get there, it matters even more that you don't skip the preliminary steps in your hurry to get to the future. Early steps might bore you, but miss even one and you might not get the chance to execute on the later ones.
My nose is fine, thanks, better every day, but the reminder was a worthwhile one.