I had a friend who was an equestrian and he'd like to take his horse on free rides on weekends - one weekend the horse just threw him off and he fell on a rock - took about 2 hours before his family found him and took him to the hospital. He remained in a coma for 8 months at the age of 21 - his life has never been the same since although he's well today, his decision-making was a little warped for a few years after that.