Horses can be very suspicious animals and when something has frightened them they tend to remember it. You have probably experienced a horse that every time they get to the place where they were first scared they expect something to happen.
Horses are very location specific in the way they behave and are quick to associate a certain place with their behaviour. Almost every arena has a ‘scary’ place in it and typically it is as far away from the gate or barn as you can get. This is no coincidence - the further away from the barn (which represents the safety of the herd to your horse) it gets, the more unsure the horse becomes and the stronger its urge to run back to safety. In some cases it may be good to avoid a trouble spot, like when you are first warming up a fresh (or volatile) horse or if you have questions about your ability to control the horse if he spooks.
However, at some point, in order for you to have total control over your horse, you must be able to take him into places where he may not want to go, maintaining his obedience. If a horse comes to believe it has a say so in where you try to take it, your authority will gradually erode to the point that you can’t leave the yard or take a circuit around the arena.
When a horse is spooky or frightened, the best thing to do is turn him toward the scary object and ask him to stand, take a deep breath and relax. You should reassure your horse by using a soothing voice and by rubbing his neck. Make sure to take a deep breath yourself as this will show him that you think everything is OK and that you have it all under control and he need not be afraid. Try to avoid turning your horse away from a scary object while he is still frightened because that will almost certainly trigger his flight response.
With an emotional or volatile horse, I would begin working in the ‘safest’ part of the arena, using small circles and lots of changes of direction to build confidence and obedience in the horse. The more you change directions and cause the horse to swing his neck from side to side, the calmer and more compliant he will become. With this in mind you will find ‘S’ shaped turns more productive than circles. As the horse relaxes and gets more comfortable, start expanding the area by venturing toward the scary place gradually and always returning back to the safe place to build confidence. Eventually I would be working closer and closer to the scary spot until I could ride the horse into that area without a reaction.
There is a very effective technique to use when working with spooky horses. First, keep in mind that you will always have more control over a horse when his neck is bent; when it is straight out in front of him he can get away from you easily. So as you approach the scary area, you’ll want to keep his neck slightly bent to one side or the other. An easy way to accomplish this is to ride in a serpentine pattern doing constant changes of direction.
Make sure that each and every time you turn you turn towards the scary place and not away from it. Weaving back and forth and turning him toward the scary spot will accomplish several things. It will keep his neck bent for greater control, it will keep him in an obedient frame of mind because he is responding to your directives and going where you said, and it will put him a little closer to the object every time you turn while preventing him from bolting.
When a horse is frightened or spooky, he needs the rider’s calmness and reassurance to let him know he will be OK. I would put my hands down on a horse’s neck to steady him any time he became tense or unsure - it is not really a reward, just a reassurance that I’ve got everything under control. I also give copious praise to my horse by petting him on the withers or neck when he is obedient and brave in the face of a scary thing.
The rule of thumb with horses is that you have a three second window of opportunity to reward, release or punish, in order for him to make an association between his actions and your actions. It follows that the sooner in the three seconds the better. If a horse is rewarded in a timely fashion he will remember it for a very long time. The important part is not whether or not he remembers the reward, it’s whether he made an association between his actions and the reward. If the association is made he will remember it for some time - horses have exceptional memories.