Never stop learning about everything that has to do with horses. Learn from experienced trainers and horse-keepers that you trust.
Take care of your own body. As a rider you could have your own pelvis tilted, and thereby your own SI- joint problems , after falling from horseback! This could affect your riding in a negative way, and also the horse. If you are assymetric yourself, and thereby put uneven load on your horse, it could interact with the horse's problems, or even create some! Seek chiropractic help when necessary.!