So I've been biking most of my life and I almost never wear a helmet. Not because I don't think they would help if I hit my head on the ground, but because in the past 20 years I haven't been injured while biking once. Maybe I'm just lucky, but I think 99% of it is just being cautious and aware of my surroundings while riding. At this point riding without a helmet is simply a risk I'm willing to accept.

(knock on wood)