As you become a better rider and get more in rhythm with your horse, you can use that rhythm to influence your horses.
For example get a partner and have him stand in front of you, put your hands on his shoulders and have him start to walk in place. As your partner walks in place, get your hands in rhythm with his movements, your right hand going down and pushing down on his shoulder, when his right leg is on the ground and your left hand pushing the left shoulder when his left leg is on the ground. As he moves along, change your rhythm by pushing down harder on his shoulder in rhythm with his movement. When you put more weight on that leg it slows his movement down. Additionally if you try to hold his leg on the ground longer, you will slow him down.
When you ride a horse, you can influence your horse's rhythm by how you move in the saddle. If you are in rhythm and balanced on your horse, when you change your rhythm slightly, the horse will detect that change and change his rhythm also. Initially he may want to slow down, stop or be confused, which indicates he is feeling your rhythm. As you work with this concept you will be able to influence his rhythm. Your horse will eventually learn to accept your rhythm as his own.
The second way to influence the horse's rhythm is by using your hands on the reins in rhythm with the horse. Maintain light contact with your horse's mouth and move your reins in rhythm with the horse's movement. When you change the rhythm with your hands, the horse will start to slow down because the horse's timing and yours are not the same. As the horse begins to understand, he will accept your timing. You can influence his speed and rhythm. Practice every day on influencing the horse's rhythm, and you will become excited about the changes you can make in your horse.