I don't know how you've been raised to think about horses or what theories you may have developed about how best to train and work with them. This is my opinion after all that I've seen and learned about horses, from horses so far. The biggest thing that I can tell you is that when I listened only to the human voices and advice, Joey and I were much more confused and frustrated. But when I would actually take the time to listen to the horse and open up my mind to what it could possibly be thinking about the situation, things became so much clearer and progress and success is usually inevitable. Like I said: this is my opinion; you can take it or leave it.
It sounds like your mare could have people problems worse than her owners having horse problems.
I don't know how she handles on the ground. If she's wonderful and just lets you do anything and everything with her, then we won't have to start from square one. But if she's a little standoffish or wary of you then I would suggest that you spend as much time as possible just hanging out with her, letting her know that you're not the bad guy. I've found that horses are really just like everything else in life in that you get out of them what you put into them whether it's time, effort, or affection. I don't know if you'll be willing to spend time just hanging out with her, but I'm telling you what I've learned is that it helps a whole lot. We've got to take into consideration where she's been so far in her life. If it's been rough for her, either due to stupid people or her own nature, then you've got to set a different standard. You've got to help her realize that she can trust people, and she can trust you. I believe that gaining that trust is the first step to getting her to ride smoothly for you.
Next I would say that you need to be able to bet your life on her brakes before you start working with the speed (even trying to downsize it). If the only speed she knows right now is full-speed, then logically you're gonna need some reliable brakes so you both don't get hurt like before. Since the only forward motion she seems to know is run, then let's try backing up. You can stop from back up, so let's give it a go. I just recently taught Joey how to back because he hated it and normally would only do it if I was super rough and loud with my cues; and even then, he was angry with me while doing it. I knew that wasn't right, so I tried to think how I could get him to be more supple and consistent. Guess what worked? I had to get supple and consistent in my cues. Horses can feel the slightest movement or touch. So we went back to the beginning, to the softest cue: I shifted my weight backwards in the saddle. At first, it was an obvious shift, just to let him know we'd changed our tune; but now I just have to think about shifting back, and he gets it. So I shift; then almost immediately on top of that cue, I pick up the reins ever so slightly (not pulling them back, just picking them up); and then almost immediately on top of that cue, I gently bump my legs in a steady rhythm against his sides while saying "back" or "back up" in the same voice. Everything has to be the same every time I do it; you'd be mighty surprised at how observant horses can be to detail. And I'll let you know that I'm somebody who is hard-wired to try the quick-fix system. But it is true what they say: practice makes perfect. And the more Joey and I work on backing, the better we are at literally backing up, or even just slowing down from a faster, forward gait. It really does pay to be soft and consistent. I've tried the harder, "more dominant" methods out there. But I've found that this works the best; and Joey and I are both having a ton of fun by the end of a ride that may have started out less than perfect.
After you can rely on Babe to back up at the slightest pressure (and stop from that backing up and stand still), then I would begin slow work on getting her to move forward without becoming a frantic racehorse. Keep in mind that this may take quite a while to work through and get right for her. It may really depend on how much time (and affection) you put into her.
Like I said: Joey used to be very much like your mare. It was either we stood still or we galloped around the paddock; there was no happy-medium. And since she responds so well to heavy pressure, this is where you'll really have to pay attention because we want her to respond to light pressure. We want her to respond to light pressure, because the slap with the reins seems to make her frantic and take off (at least that's what it did to Joey: it made him get super tense). I have a dressage whip that helps me in this department. But just a long-handled anything could work (preferably with something ticklish on the end). Again, I would start from the beginning with the softest cue: a squeeze or bump with my calves just behind the cinch. He didn't respond, so a squeeze with my calves and then a slight tickling or teeny-tiny tap with the whip. That would usually get him to wake up and pay attention. Maybe he wouldn't move off just yet; so I squeeze again, tap a little harder with the whip, and now he may be ready to jump out of the starting gate like he used to, but here is where I do something different: instead of tensing up, ready for that jump, I stretch my spine up and my heels down into my stirrups in balance and I shorten my reins gently and softly massage the reins until he slows back down. Sometimes I have to sit deep in my saddle and roll with him while I massage the reins if he decides to be hard-mouthed. Bring him back down to a halt and start again. If you work at it enough and are soft and understanding every time you do it, eventually your mare won't tense up anymore which will then let her be able to go from fight-or-flight mode to thinking mode: "Hey, I wonder what he really wants me to do?" The key is rewarding every time you feel a try. Even in backing up or stopping, a try might be just a teensy shifting of weight. But you've got to be on the lookout for even the tiniest try, and reward it. You'll gain success and progress much faster if you keep your eyes open like that. And then build on the tries. To begin with, you might reward a slight shifting of weight in the correct general direction; but after that you can wait and reward her when she takes a step in the correct general direction after shifting her weight. You see what I'm getting at? And rewards can be anything from a pat on the neck, to a generous word of praise, to the complete release of pressure, or even a cookie. Joey responds much better and tries much harder if I notice even the slightest effort and give generous praise while we're out riding, even if it's for something that he should have already known how to do.
Another key is to give your mare a chance to respond to your cues. After you squeeze with your legs, give her a second to try and figure out what it is that you want from her. More than likely at the beginning of training, she won't think for herself, because she's expecting you to just slap her and tell her what to do. But if you consistently give her even a millisecond of chance to think for herself and respond, she'll get it that much faster.
I'd love to hear your opinions on the matter, so leave a commet below sharing what you think!
~Sam and Joey