Until I can dredge up actual memories from college (which I assume there must be some) I will tell something from childhood.

My family went on a yearly camping trip to go fishing and mountain biking and other camp type things. When I was pretty small proably 6-9 I do not remember the age, I went to go ride a trail with my older brother (4 years older) and didn't put a helmet on. We get to the trail (which is flat mind you with gravel and small rocks) and my brother asks me where my helmet is which I promptly tell him I forgot it, he gives me his (which was an old one that was hardened styrofoam circa 1990~) and we start riding. I get maybe another twenty thiryty feet down the trail and find the one big stone to ride straight into, stop dead, and fall over. Brother checks to make sure I'm okay and i am and we continue the ride. We get back to camp and my dad asks why my brother doesn't have a helmet on, he retells the story and then my dad asks what happened to the helmet i was wearing. He then points out a rather size-able divot in the helmet that almost went through the 1 inch or so thick helmet.

Thank god that rock hadn't found my skull without a helmet, and for my brother looking out for me.