...bsms, you are right--every horse is an individual, and some will listen well without a bit, and some won't. I would NEVER ride Corporal without a bit. He LOVED to run, even in his old age, and couldn't be trusted without at least a snaffle in his mouth...
Mia & I were out today with Trooper & my daughter. The weather has cleared a section of trail near me about 1/3 mile long so that it has no significant gullies and no big rocks. My daughter wanted to try a canter, so I put Mia in front, told Mia she was a ham-hoofed POS who probably couldn't trot - that being our normal signal that a canter is imminent - then asked her to go. She went. Leaped into a canter, and about 5 strides after that switched into a gallop.
In her defense, based on what I can piece together, it is likely she hadn't ever galloped in the open before (apart from bolting). Her life has been filled with corrals and small arenas. With a trail opening up ahead and a rider who wanted something faster than a trot...well, she delivered.
She loved it! You could see the light bulb go on above her head. "I'm a horse, and I'm strong, and I can go fast!"
However, the trail takes a sharp 90 deg bend at its end, and Mia isn't known for graceful turns. Slowing her down was a challenge. It took about 50 yards to get her down to a canter, and another 50 to get her down to a trot.
Then she behaved like a lady. Trot, walk, jog - anything you want, bsms! So we went back to the beginning and tried again. And...
"I'm a horse, and I'm strong, and I can go fast!"
In fairness to her, I gave her her head most of the way. But near the end, my thighs went against the Aussie-style poleys and I WORKED to get her to calm down!
And again, after we stopped she was a lady. "Anything you want, bsms!"
When we got home, I asked her for a canter around the arena, and she picked up a relaxed, controlled canter. But I think she discovered that "I'm a horse, and I'm strong, and I can go fast!"
FWIW, she had a full cheek snaffle today. I have no idea if she would have responded to a bitless bridle, but I wouldn't bet on it. And yes, it is a training issue. We've had training issues for 4 years, and they are not over. But Mia may end up like Corporal...running today, I could feel the joy in her body. She was as nice and as willing as could be today, after we slowed down. But when asked to speed it up with an open trail ahead of her...she was happy. Very happy. Oh...and Trooper?
My daughter lost her stirrups both times, and Trooper slowed to a trot the moment she asked him to, even with Mia out ahead opening up the gap. Trooper is still "just a little trooper", as the saying goes that gave him his name. Thank God not all horses are like Mia, but I admit to being thankful that Mia IS
like Mia. Whatever else she is, she isn't dull...