I think what you have to remember is that accidents, being accidents, happen when you don't expect them. I actually think I have more accidents when I decide to take it easy and dawdle along, you either relax too much, let your body position go (as a relative newby I still have to think about these things). My last off happened because I'd decided to go easy and was braking somewhere I'd normally be going flat out.
The first time I wore my Smiths Mainline I only wore it because I was going for a "proper" ride after escorting the OH at the time out on a young horse for familiarisation. Some moron came past the other way at 110kph on a country road missed us by mm's , scared the horse which panicked, leapt in the air, span round knocked me off and jumped on my head. It fecked the helmet and I had a pretty sore head, but if I'd not had it on I'd be dead.
Fortunately, a lot of the gear we can buy now to protect ourselves isn't hot or restrictive and most of the time you don't know you have it on.
A recent example of an accident when you don't expect an accident from a more experienced rider.