I applaud you for getting a trainer to help you.
It's good to have experience before getting your 1st horse. It don't always work like that for so many of us, myself included. I too got my 1st horse that was green while I was a green rider. I bought my appy from my trainer/riding instructor who thought we would be good for each other and learn a lot together. He need a lot of long rides and concentrated training. I didn't have the knowledge to do all that, but my trainer was there for me when I needed her. She worked with my horse, on the ground and in the saddle. She helped me understand feel and timing when working with him. She taught us a lot, but still he was spooky an reactive, but he never reared with me on his back. He did a couple of times on the ground.
I was watching some Clinton Anderson dvd on youtube and RFDTV. He kept talking about horses having holes in their training and getting your horse to respect you as their leader. I had read the same thing from many here on the horse forum, but didn't know what steps to take to get where I needed to be.
I got the fundamental kit and started from the beginning retraining my horse. He's now one of the calmest horses I have. I've been riding a little over 2 years and have 3 horses. Since I acquired some of the knowledge I needed to really move their feet and get them listening to me, I have no doubt that Vegas, the stubborn appy, is my heart horse. I just had to learn how to bring out the best that was within him. I have only scratched the surface, I still have a long way to go.
You know what? My trainer was right Vegas and I is good for each other. Because of him and his reactive nature, I did my homework and we learned a lot. I do most of my reading right here on the horse forum. I do all of my research for any problem that may arise here and I always find the answer. Then I go back to the fundamentals to make sure I know how to apply them.
Good luck and have fun with your horse.