Does it really matter why it happened in regards to the helmet? The helmet did save some addition pain and trouble. I think in regards to skills we all are improving all the time. My big crashes were on my mtb and i am learning all the time, my comment about the big crashes was only to say stuff happens and you should factor that into your decision! I don't personally care one way or another which way folks decide but in my opinion why not be ready when the cat jumps under you at 20 or 30 or you end up run off the trail and break your back and tailbone. Would have been much worse with a head injury also!