Horses are prey animals. They only fight when they can’t flee. So nervous or frightened horse would be more likely to rear or buck in a round corral than it would in an arena. Remember that.
Its important to be able to read a horses body language when riding. For example, if your horse stops with its head upright and its muscles tensed, it most likely caught a glimpse of something strange and is ready to turn and run should anything attack it.
Horses can read your body language just the same as you read theirs. If you come at a horse with your hand raised and leaning into your “march” he will hold his head higher than your hand and back away quickly. So learn to come at him softly, walking naturally and lowering your hand. After all, what horse would want to come and be caught by a scary monster?!