I just started riding a 7 year old QH who looks like a TB and he can act like one too! Our first ride was quite the experience.........he got all fizzy on me and reared. It felt like I was sitting on a loaded barrel of TNT! I don't get on him as much as I wish I could, but I can tell you that he's already gotten better. We came to an understanding that if he didn't rear I wouldn't make him do tight circles. He still gets fizzy, but with work he has calmed down. All this to say, give it time and be persistent. Do as much as you can with him on the longe, on the ground, and in the ring. Alot of easy walk/trot work, lots of circles and serpentines. He will come around. I know Buck acted like that because he didn't know me and hadn't been ridden in over a year. We have alot to work on, but I can say he has come along well so far in just a few weeks. I agree with all the others that it's a good idea to make sure all injuries are well healed and nothing hurts.