When I was just learning to ride back in 2007 I tried out Horsetoothe Mountain Park by Fort Collins.
The trail is an advanced trail and after spending several hours climbing/hiking my bike to the top I was exhausted! The first bit of down hill on the trail is a tricky rock garden that is very steep. I was riding down the face of a rock with all my weight over the back tire and laying on the binders when my front tire hit a loose volley ball sized rock and sent me over the handle bars. As luck would have it I was at the top of a 3 foot drop so not only did I fall the distance of my bike at speed but I also fell the additional 3 feet onto hard rock, head first.
When I regained composer and looked over the yard sell of my equipment spread out over the trail, I realized my helmet was shattered, my right arm was badly cut open, both my hands (no gloves) had huge gashes, and my right leg had serious road burn up it. Luckily there is a service road that goes to the top which offered me a smooth easy ride back to the car. My arms still have the scars but other then that I am still riding and have tackled that section of trail numerous times since!