When a horse is initially trying to figure out something, there is a distinct lack of clarity in its mind about what are its best choices when confronted with pressure.
The horse world is awash with training methods for every aspect of dealing with horses from handling foals to competing at the highest levels in any given sport.
Do as much homework as possible on anybody you allow to interact with your horse. Do as much preparation as possible before you allow somebody to work with your horse.
I am a huge fan of teaching a horse to follow the feel of the inside rein and offer a lateral bend through its whole body. One of my most regular Ross-isms at clinics is “The bend is your friend.”
Why do so many serious dressage riders I know dare not take their horse on a trail? Is it because those horses do not have the makeup to be safe on a trail?
Problems with a horse are not fixed because we want them fixed it. For things to change with our horse it must begin with things changing with how we work with our horse.