My TB puts his head down and stretches a lot, especially when I'm riding. I know it's a good thing and my trainer told me to reward it, which I do, but he does it constantly. It's usually at the trot and he stretches way down to the ground about every ten seconds or so, and it goes on for the whole ride some days. Should I let him stretch as much as he wants? I can't really do much when his nose is all the way to the ground.