It's impossible to overstate the importance of a well-trained human to the happiness of a horse's life. As with anything, you can cut corners and start with an untrained human -- or even try to reform a spoiled one -- but unless you're an expert, it's a risky thing to do.
Cry if you want, but you'll learn to sit that trot!
So I think I'm pretty lucky, since my particular human, Lil, came into my life beautifully trained. Some of it was thanks to other humans, especially the riding coach she had as a teenager who was totally old school (Hungarian cavalry) and liked to drill his riders like they were conscripted soldiers. Riding without stirrups is, I'm told, fairly painful, but it sure makes for a terrific seat, and getting yelled at anytime you make a mistake helps you to develop your riding pretty darn quickly. And don't even THINK about blaming your horse for knocking down a rail or missing a lead-change; the old-world coaches put the blame for every mistake precisely where it belongs -- with the rider. Evidently one of Lil's fellow students ended up in tears at least once each lesson. That kind of discipline either makes you a pretty good rider, or you switch to lawn bowling.
Oscar adds the finishing touch
But of course the best training comes from horses! Now some of the horses from Lil's youth left their marks (physical AND psychological), but young humans are vain enough to think they're indestructible, so they're not always teachable the way older humans are. Getting dumped in the dirt makes much less of an impression on a twenty-year-old human than a forty-year-old one. So much of Lil's most valuable training came much later in life, mostly from Oscar, the aging Irish Thoroughbred she still had when I came into her life.
Oscar was very tall (17 hh), quite attractive in that skinny-legged way some humans find appealing, and very, very cowardly. Water, unless in a bucket or trough, had to be avoided at all cost, and deer, pigeons, plastic bags, snapping twigs or a sudden gust of wind were cause for panic. He had a nasty "spook" -- dropping one shoulder, spinning and galloping off in the opposite direction. He never dumped Lil (see riding without stirrups, above), but dumped lots of unsuspecting riders (from great height!). He made every ride an adventure. Eventually, his humans learned to anticipate a potentially scary situation from his perspective and often "spooked" before he did. Oscar could turn a calm, easy-going human into a twitchy bundle of nerves in no time.
Besides being a chicken, Oscar was also a hypochondriac. He liked his Banamine, and knew how to get it. If any horse in the barn got sick, Oscar developed sympathy pains and had to get his drugs. Once a mare mis-carried a foal at the stable where Lil was boarding him, and Oscar was sick for three days. He hobbled like a cripple after a foot-trim that didn't include shoes, convincing the barn manager that his stifles were locking up and he needed rest, an expensive vet call, and more drugs. The result? Lil became a finely-tuned horse-human, anticipating every danger and reacting to every muscle-twitch and stomped hoof. I had her phoning the vet once just by circling my stall and pawing at the floor when we had to stay inside to wait for the farrier. Could it be colic? Sure! Or just me, messing with your head!
Consistency is key
It takes years to train a human to this level, and only a few months to spoil it all. My Friesian brother Wilby (ok, he's not really my brother, but we're all related somewhere along the line) came dangerously close to undoing Oscar's hard work. He's a total goody-two-shoes and too trusting by a country mile. He'll turn himself inside-out trying to do what the human asks him to do. Before long, Lil was losing her edge, and we (horses) had to start looking out for horse-eating lions in the arena ourselves. But I fixed that problem by convincing Wilby that a whole colony of nasty ghosts lived by the big back door of the arena. He's pretty smart, that Wilby, but awfully gullible. Now he's beautifully jumpy around that end of the arena, and even dumped a young lady not too long ago by spooking when the wind rattled that door as they were cantering past. Of course, being Wilby, he immediately trotted back to check on her and apologize by sticking his nose in her face.
But I'm still working on him.
The lesson to be learned is that if you're lucky enough to have a well-trained human in your possession, you must be very careful not to let her slide back into comfortable old habits. You must keep her reflexes razor-sharp. And if you let less advanced horses work with your human, be sure to "tune her up" after every session. It's the secret to a happy horsey life.