Head knocks are over rated, if you're not right you'll know instantly, but everyone is all about being careful. Your trip late on sounds similar to my catastrophe at langdale coming down to blisco, you fail to lift your legs up high enough due to fatigue. I tripped and after flying through the air was stopped by a chunk of quartz at full descent speed. It was very hard work finishing the race as it hit me in the thigh and the scar looks to be permanent.