^^^ That's what happened to my friend. He a very good rider, good enough that I trust him in teaching me how to ride. But like he said yesterday, "I was being a dumbass. I've never had a problem when I've been riding smart."
For me, there are sometimes that I get somewhat comfortable on the bike and then the thought will creep back into my head like "If one thing goes wrong, I could be in the hospital." That's kind of scary. However, riding is so amazing I can't stay away!