I ride casually, usually to go work out or a 7 or 8 mile ride in the evening around town. The town has put in some bike paths which are very welcome but very crowded at times. Last Sunday evening I came up on a couple walking on the bike path. So I rode off the path and after I got by them I wiped out trying to get back on the path. The bike path's surface was about 2 inches higher than the ground level. The grass was high enough that I didn't notice until my front wheel hit it. As I was falling I extended my hands to break my fall and I thought for sure I'd break my wrists. Luckily I didn't. I have a really ugly looking right knee. Plus other scrapes elsewhere. While I was lying in the weeds, face down the guy I just passed said "are you OK, sir?" Sir? Damn it, I was face down in the weeds with a bike helmet on and I still looked like a sir to him! Hurt worse than the scrapes.
Wear a bike helmet, regardless. I popped my head pretty hard and it saved me from much worse injury.