A great exercise to practice is bending transitions.
In this exercise, you’ll trot your horse on a loose rein and then transition him down to a walk, asking him to bend his body as he walks in a circle. It’s important to practice the exercise on a loose rein so that you’re not masking your horse’s problem by holding him back. Dare him to make the mistake. Even if you know he’s going to speed up, you have to let him.
Once your horse is trotting forward on a loose rein, bend him down to a walk by sitting deep in the saddle and taking your legs off to warn him that you’re about to slow down. To bend him to the left, slide one hand down the left rein and pull it up to your hip. At the same time, press the middle of your horse’s ribcage with your inside left leg to create bend in his body.
Good luck !