We went on a trail ride one day. Most of the riders at the barn we keep our horses at, don't wear helmets when trail riding. For whatever reason, this particular day, I decided to go against the grain and wear mine.
While we were out, a storm blew in causing my 12 year old Tennessee Walking horse to rear up in a tight trail spot - this pushed him into the brush behind him and he bucked - to me it felt like he was falling so rather than getting caught up under him, I rolled forward off his shoulder and onto the ground. I landed on my upper shoulders and back and I could hardly move.
My friends took me to the emergency room where they took 20 xrays to make sure I hadn't broken or fractured anything. The staff kept telling me it was a good thing I was wearing a helmet! I will never ride without one again. It only takes one time to permanently injure yourself or worse!