On my 18th birthday, I was out biking with friends down
mount Sir Wilfrid near my home town. It was ATV/snowmobile trails and at some point we were going down quite fast when I lost balance forward just before a steeper grade with a sharp turn at the top, I rolled a bit on my front wheel till it met the side of the trail and sent me flying over the handlebar. I landed head first on a large boulder. The helmet completely broke off in three parts and I cracked a vertebrae, but I'm still here today.
I have always been wearing helmets when biking, skiing and snowboarding, even back in the days when I was a kid and no one was wearing them, but my dad forced me to wear one. Helmets saved me numerous concussions and probably my life 2 times.