I’ve crashed my CBR 600 F4 twice on slick pavement (and I was going to fast). The first time my head BOUNCED off the pavement. Thankfully I was wearing a full face and just I was a little woozy for about 15 minutes. I shudder to think what would have happened to me, had I not wearing a helmet.
You're very smart for wearing one. It has saved many riders. The macho types figure it'll never happen to them.
Depending on your age and physical condition, you would have died.
I've seen guys without helmets plow into the back of a car at a (relatively) low rate of speed. You may not get a severe head injury, but its good for a broken jaw and worse. So not only do you need a hemet, but one that protects the entire head (is that what you call full face?).
Not wearing a helmet, even on a bicycle, is stupid.