Learning to ride horses can be a very difficult thing to do. Many people if they have difficulty learning something just focus harder. Focusing harder has a negative impact on the horse. Horses are creatures of flight by nature so anything intense like hard focus, fear or anger can cause problems. Riders will ask: "What am I doing wrong?" I will have to say technically nothing, but the focus intensity is too strong or anger or fear is present.
Fear shows up when the horse is too advanced for the rider. Maybe the horse is too sensitive and reactive for the riding level of the rider. Or maybe the horse is too large and in charge and tests the rider for his or her own amusement. In this situation, enlist the help of a trainer to help you through it, or decide if a different mount would be more appropriate.
Anger shows up when the riders have a certain idea of their own talents. Horses show the riders that they do not know as much as they thought they did. Riders then either go into very hard focus or outright abuse. Either way both the horses and riders lose.
Some riders actually go into hard focus innocently, because they learn best in hard focus instead of soft focus. The problem is that the horse is afraid of hard focus - so the rider has no choice but to learn to go into a soft focus to get the best out of the horse.
Do your horse a favor and practice soft focus - you will be surprised at the willingness to learn that your horse will offer in exchange.