most people don't want to accept that they're not as light as they THINK they are, OR, don't want to take the time to go slowly with their horse. I know a lady that went through literally dozens of bits on a horse that for me, never needed anything more than a ring snaffle, or a bosel.
I heard 'my horse is tossing his head - why does he do that?'
I would say - you're too hard with your hands. Lighten up, and go back to the round snaffle. Which was always immediately followed by 'oh no. I know I"m being very soft'. OK. This kept up until she had him rearing up. Then it was 'why is he doing that???' I said 'like it or not, you're too heavy handed. Put him in a hack or a bosel, and keep the hell out of his mouth if you can't lighten up'
Course, she wouldn't listen to that until she'd heard it 4 or 5 other times from other people. Leaves you thinkin' wth???
Ask Often, Demand Nothing, and Reward Generously.