Training horses is not supposed to be mortal combat. We are expected to be smarter than they are. (If the reverse were true, they would be "riding" us, right?) Ideally, we use our bigger brains to make learning seem doable and feel non-threatening to our horse.
Here are the rules of thumb for "riding smart" that I've accumulated over the years.
You can’t train a horse that’s hurting, so rule out physical pain. Whenever your horse is being stubbornly resistant, make sure it's not because he's in pain.
Is he not stopping well? His hocks may be sore.
Resisting a spin? His suspensory ligaments (the structures supporting the back of the lower leg) may hurt, or he may have bumped his knees together, making them tender.
Tossing his head? His teeth may need floating.
Always check with the appropriate expert—a veterinarian, chiropractor, or equine dentist—to rule out a physical problem whenever you hit a roadblock. Only after you get the green light should you push on with your training. To head off problems, I have my horses checked regularly by my vet—I don't wait until one starts resisting.
Maximize every moment. Whenever you're with your horse, you're either training or untraining him. If you're picking out his feet and he's dancing around or leaning on you, don't let him get away with it. If you do, you’ll set an "I'm the boss" precedent in his mind. Instead, take the time to set his priorities straight by insisting that he stand obediently when you ask. If you're riding him through a gate and he won't move laterally off your leg, school him until he does. If you're going down the trail on a pleasant morning and he's pulling on the bit, don't think, "Oh, it doesn't matter now." It does! All these random moments add up to a lot of good training; don't waste them.
Set him up to succeed. A horse must understand and accept an idea before it can become his own, and only then can you train him how you want him to do it. Another way to think of this is that you must show him until he understands and accepts a maneuver, and only then train him on it. It’s a subtle but important distinction. And only when he gets it can you go on to ask for speed. If you push for speed while he’s still confused, he’ll come to resent what you’re trying to teach him, or at the very least become badly rattled.
So use your aids in a way that enables your horse to find what you want, rather than forcing him to do your bidding. Yes, hauling on the reins is one way to get a horse stopped. But how much better to lope him until he’s a bit tired, so that when you pick up your reins he wants to stop. Help him figure it out, and give him time to do so, then reward him when he does the right thing. Your horse must have confidence that if he needs a moment to think something through, you're not going to get all over him for it.
Once he’s figured out the what, only then can you start teaching him the how. To use the stopping example, that includes getting his hind end up under him and not leaning on the bit while he does it.
Think back to your school years: did you learn more from the teacher who rushed you, then bullied and humiliated you for a wrong answer? Or from the teacher who set you up to find the right answer, then told you how clever you were when you got it? In the same way, if you help your horse when he’s confused—instead of hammering on him—he’ll start to think of you as a friend he can look to for guidance when the going gets rough.