When I cut, I wear the helmet in my little wagon below. I honestly only wear it because it has the earmuffs and front screen on it. I was clearing the area around a Ash Tree I was going fell. There was a small dead tree about eight foot tall and about 3 or 4 inches in diameter with top broke off. I cut it and it seemed like it was gonna fall away from me, so I looked away for a second. Then it fell and hit me on the top of my helmet. If I didn't have the helmet on, it probably would've knocked me out. Instead, I didn't even get a headache!
Good you had it on. I have a similar one I'll wear on occasion for the same reason usually at my Disney job. Felled a dead ash years back and had a limb fall very close to me when it went over. I had almost no escape path. Thinking back I shouldve worn a helmet. I've learned to always look up first. Experience is great teacher.