My baby girl was a very spooky horse. She is a High thoroughbred content QH. I have fallen off of her so many times that I have lost count, and I still have trouble trusting her since she gave me a concussion a year ago.
We have incorporated a few things since then. Lunging before I ride helps her get the bucks out, and if I can’t do that, I do in hand work to get her mind in the right place. In my experience, getting her mind in the right place is much more important than getting her tired. I don’t know about your horse, but I would suggest walk and trot lungework, focusing on stretching and getting a rhythm. The way I tell if Frosty is ready to be ridden is if she stops looking around and doesn’t give me the “Oh my, there are dragons!” Look. Then I stop the lunging, reward her, and tack up. But regardless, I Always try to get her mind in the right place.
Just my experience. It may or may not help with your horse. I hope I could be of some help.
Dressage is a dance, where horse and rider speak with silence, Where force is not necessary, and where the horse trusts his rider completely, even in the middle of the battlefield.
-Amber Blyledge, 2016