About 19 years ago, I didn't wear helmets, only when truly needed. One of our foals I was training was noted to buck whenever he wanted. He is one I always wore a helmet with, he threw me in the middle of 30 cows, and a few other times. The main point of this post.
One day my dad said enter him in a gymkhana and let him run, I did, he bucked so hard there was no way to stay on. I woke up in the hospital, the doctor brought me my helmet to say you were very lucky you were wearing this helmet. It was split in half. After that no matter what horse I am on, I wear a helmet. That geldings sister is my main mount and trust her with my life, BUT I always wear my helmet