A couple of weeks ago I gave a theory lesson for my students who are all primarily in disciplines other than dressage. I was pretty excited about it and my students kindly indulged my enthusiasm. We covered the basics from why we even bother with "dressage", the training scale for the horse and for the rider, to the aids in general and for the leg yield and lateral work in particular. While I always talk about the "why" in my lessons, I know how focused a rider needs to be when working on their own body while trying to also successfully influence the horse. A bunch of theory will naturally be tuned out. But it's so important to know the bigger picture and to be able to be very precise in the aids. Understanding them clearly is a big first step toward being able to apply them properly. It's always so much more complex than "inside leg at the girth, outside leg back." If that was all there was, everybody could ride a Grand Prix test in their first three months of riding (which is why I also covered the training scale for the rider.)
But understanding the connection between the horse's ability to bend and lift his legs, and his alignment in relation to balance and suppleness, are crucial not only in helping us address every horse's challenges in particular, but also in making us more compassionate riders. I think the less experience riders have in seeing and understanding this complexity, the more they are ascribing behaviors, especially unwanted behaviors, to personality rather than seeing them as a logical consequence of physicality such as a tight back, misaligned pelvis or shoulders, a very dominant left- or right-handedness etc. Added to that equation is the kind of work the horse performs regularly, and in what alignment.
I am not at all saying that horses don't have personalities. On the contrary, I find them to be amazing individuals who are almost all incredibly cooperative if treated fairly and compassionately (and a lot even when they are not treated that way.) And by fairly and compassionately I mean by understanding the very physical limitations they are currently displaying due to the above mentioned issues, and addressing those gently, correctly and consistently through the gymnastic exercises outlined in the classical works.
A horse who consistently sticks his head up in the air, for example, in a trot/canter transition, isn't able to do it better because it's not in the right alignment and balance. And generally not because he's a jerk and/or hates dressage. Try to do a good cartwheel with one arm sticking out forward/sideways and one stiff leg sticking out backwards. There are a lot of "lazy" horses that are only "lazy" because they are misaligned and have trouble bending their joints, hence can't move fluidly and easily. Help them into correct alignment and improved suppleness, and stiff and lazy turns into forward and beautiful.
Being able to diagnose a horse's physical gymnastization needs also takes emotion and ego out of the riding. Training is not a battle, it's a physical therapy session. And of course, some horses, depending on their issues, can offer some very challenging behaviors. But anything but the real work won't fix them. Short cuts might cover up a symptom, they won't make for a happy, healthy, capable and reliable partner that can do his job for many years to come. And after all, that's what we want, isn't it?