Why you should always wear a helmet, especially if your head is not on straight

When I was eighteen, the summer before I started my full-time factory job, I took a summer school course at St. Thomas Moore. Surprisingly I wasn't a very good summer school student; I got my lowest mark ever in high school and only did well on one test that was total review. I didn't study that much either. Every morning that July I would bike to school in my jeans. It was hot and I would get extremely sweaty before I arrived in the air-conditioned school. Since I wasn't a great student, the teacher gave me special accomodations and allowed me longer to take the test. So one morning I was biking to school early so I could begin the test before the other students. I was about to turn into the school when I noticed a car beside me. Stupidly I thought the car was also turning and even more stupidly I thought we could turn at the same time. So the car hit me and I flew over the windshield of the car and landed at the other side of the road; my helmet was split down the middle, I had some scrapes and bruises, but I was basically unhurt. I was ready to go and take my test, but the person whose car I had collided with was very worried and called 911. So the firefighters arrived, and insisted on cutting open my jeans at the knees to inspect the damage. I had to make those jeans into shorts; I was mad about that. Then the paramedics made me go in the ambulance to go to the hospital, although I was basically unhurt. If I remember correctly I later had to pay for the ambulance. The police took my bike as evidence and later gave me a hefty fine for turn without safety as well as points on my driver's license, although at this time I wasn't driving a car.
After a nurse cleaned up my scrapes on my arms and legs, I returned to school that afternoon and took my test. I noticed some of the other students pointing me out as the student who had gotten hit by a car. This story could have been told in a more humorous fashion, as I have had all my coworkers convulsing over the ridiculousness of what I had done. Today it sounds a little more melodramatic, but I am emotional after reading the VE section in the Spectator.
The point of this story is that you should always always wear your helmet, because you could get permanent brain damage should you be hit by a car, or should you hit the car yourself, as in my case. I haven't biked much since this incident, but I still have my bike which is slightly damaged but still rideable.