Bears like the smell of fabric softener? Serious question, as I actually DO keep a sheet in my pack. I'm rarely in bear countryThat's pretty much what I'm talking about. Since it's difficult to determine what was a bluff charge and what was an attack, many or most of the bluff charges may never have resulted in an injury or fatality anyway, so the fact that bear spray was employed and the bear turned away may be correlation without causation.
Black bears - they'll almost always turn away when confronted directly unless Mama feels her cubs are in direct danger or they're cornered somehow. Have seen terriers tree them, and I've treed several myself, many times without knowing they were there. However, have seen the aftermath of people who did stupid ******** like eat or store food in their tents - or even just carry a sheet of fabric softener to keep their skivvies smelling sweet in their pack.
Browns - different story altogether. If you're in Grizz territory - "pack" appropriately.
As far as not missing - practice, practice, practice.