I've only had one near-death experience, I was 12, and we have a swimming pool in our neighborhood, so I put my towel over my handlebars on my bike to get me going, and went with a friend. We managed to get out of our cul-de-sac, before the towel, you guessed it, caught in my wheel, choked the spokes, and put me into a 720 flip, which threw me off my bike, my chin hit my handlebars, my head smashed into the pavement, and I got knocked unconscious. Thankfully, I didn't die, because I was wearing my helmet! :D
tl;dr: Wear your helmet, or you die.