A calm horse can feel a fly landing on its butt. When my mare is calm, she stops from me settling into the seat. When she thinks she is racing another horse? Let's just say she doesn't stop for flies landing on her butt!
Ever hear the term, "has the bit in her teeth
"The earliest known use of the phrase is in John Dryden's satirical poem The Medal
But this new Jehu spurs the hot-mounted horse,
Instructs the beast to know his native force,
To take the bit between his teeth and fly
To the next headlong steep of anarchy."
In an ideal world, we would all have endless hours to train our horses, and the facilities and area to do so. But that doesn't describe my world. Horses have wills. Some don't like to go fast. Others get intoxicated by it. A french link snaffle is no more the answer for every horse than a bitless bridle is, and for the same reason.
Mia seems very receptive to adding pressure on the poll. It just seems to be a cue that she understands, and has since the first time I tried a gag bit in her. We are also doing a lot of practice stops, because an OK stop at a trot is going to be a pee-poor stop at a gallop - if another horse is also galloping. By herself, she'll stop very quickly at a gallop. But she has a mind of her own, and sometimes uses it...