When riding a horse you are in charge of two living, breathing creatures: yourself and the horse. The rider should be aware of his own actions and how they are being received and perceived by the horse. And also the reverse: the rider needs to be aware of the horse's signals to us as riders.
Sometimes horses are punished for misbehavior or resistance when he may be trying to communicate a discomfort to us. His cues to us will be almost imperceptible to start with. The rider always needs to be "listening" to the horse to prevent any discomfort. If the horse finds that he is ignored, his cues to us will get more and more "loud". Discomfort with a saddle might start with him tipping his ear back as the rider starts the saddling process. Next time, he might walk away. Sometime later, he will refuse to canter. At last, he bucks. That may be what it takes for the rider to "listen" to him.
Check to see how you ask your horse to "depart" or "walk on". Some horses who have been thumped on the sides for so long will just turn off to the discomfort, which will call for a "louder" cue. What a cycle! Looking at a different move, how do you ask your horse to turn right? Do you pull on the rein? Rather than contacting the mouth, let's set it up another way by giving the horse several pre-cues. First, focus your eyes in the direction of your turn, turn your torso in the direction of the turn, put the leg on, then lastly give a light signal with the rein. After several times of this consistant set of pre-cues, the horse should start turning as you set your focus.
Let's take a look at the snaffle and its action. Get a snaffle bit with a pair of reins attached and try this experiment to see what the horse feels when you pull on the reins to stop or turn. Roll up your sleeve, and place the bit around your forearm. Now raise the forearm vertically, and get a friend to take up the pair of reins. Get your friend to pull back gently on the reins--you will have to resist slightly to prevent your arm from being pulled forward. Now get the friend to pull harder, then harder still, finally sawing on the reins from left to right, as you will often see riders doing to get the horse to lower his head. Quickly remove the bit and see the white ring that has formed around your arm where the blood has drained out - and this is only after seconds - think how the horse must feel after an hour or more of being ridden with a strong tension on the reins. The horse’s mouth is far more sensitive then your arm. He has many nerve endings in the part of the mouth where the bit lies and acts, and in time, all of these become destroyed by harsh handling of the reins, so that the horse becomes’ hard-mouthed’ and insensitive.
Always try to be considerate of your horse as another living, breathing creature. Check his equipment fit frequently. Listen to his signal of communication to you. A rider should be firm, but with consideration.