I have been involved in horses most of my life and can tell you that the majority of them actually love racing, whether they are ponies in a riding centre or the best racing thoroughbreds. I used to run a riding school for a farmer and he also had a beautiful palomino stallion and 5 brood mares. Watching them out in the fields you would see them racing and jostling each other , for fun, when there was no one making them race at all. As herd animals they naturally bunch together and run in groups, so actual racing is something we add on to their natural ways.
We also had a particular horse that really loved jumping, and if you put him in a field with a bale of straw or any small jumps left from some training, you would see him going round jumping the jumps and then turning round and jumping in the opposite direction.