Most of us have learned the hard lessons from experience unfortunately, some lessons we learned from others bad experiences. The big thing is to learn from the mistakes. I still have a piece of steel in me from an object I was striking with a hammer. Many think you're being an alarmist or not manly by suggesting or using safety equipment.A guy I grew up with lost an eye this way, he wasn't keeping the mushrooms trimmed on his wedges. It only takes two minutes with an angle grinder or cutoff wheel to trim the worst of mushroomed heads, and really only a few seconds each year to keep ahead of them. No excuses!
I like to face mine off so they're slightly tapered in at the striking surface. In other words, the striking surface is 1/16" to 1/8" smaller than the max cross-section of the wedge, with the taper starting about 1/4" down from the striking surface. This slight taper seems to slow the formation of a new mushroom head.