I bought a TB field hunter who was like this. In fact, I bought him because he was a great hunter but his owner said “You CANNOT ride this horse on the trail or just around the barn”. He was excitable and filled with energy. For weeks I rode him in my yard at a walk, every day, with a long rein. He was always anticipating working, jumping, galloping, etc. so this shocked him. When he relaxed enough for me to let him graze with me on his back, I let him. It took time. Lots of patience. No work in the ring or anywhere. No fox hunting. Just long slow walking around, and around, and around. The next hunt season he was so relaxed that his previous owner did not even recognize him !! The fix has lasted for years. He had to find out that a saddle and rider does not mean WORK. It means RELAX and ENJOY yourself. Relax yourself and take your time. It’s a challenge for us as riders to put the theory “less is more” into our training.