In motorcycling we have a saying, dress for the accident not the journey. Something about most accidents happen quite close to home.
I have smashed up 1 helmet my son 2. Mine was due to stopping pedaling just as I crossed the finish line in a 10, should not really do that on a fixed wheel, I remember looking down from a long way up thinking this is going to hurt.
His was 1st one was when a front skewer snapped 1/2 mile from home after a 40 mile training ride in the Wolds luckily we were only warming down, Still a trip to hospital and stitches etc. no it was not over tightened just fatigued is the conclusion we come to.
Do I wear a helmet, you bet I do and full leathers when out on the motorbike and a seat belt when driving and a life jacket when sailing.