I worry more when fly fishing the high mountain creeks. It was the actual reason I bought the bear spray. Unlike hunting. When fishing the creeks the noise of the creek drowns out any other noises. Plus, i'm concentrating on the water, and not looking around at all. It would be simple for a bear to walk right up to me, and i'd never know it. The last bad thing is that's where bears hang out is around the water.
I never worry while hunting, because they couldn't sneak up on me, and i'm carrying a gun if they do. If I was a bow hunter. The bear spray would be enough, but even then. I'd have a bow.
Hard to stop a bear with a fly rod.