Then what is the point of dressage??
That is always a good question to ask oneself...why are we doing this? Is it to teach movements? Or is it therapeutic? Or to have fun and Win? Whichever is your priority, it's good to remember that others may have different priorities; surely we can agree to disagree on some of this.
My question still stands. How do you relax a tense horse before you go to work?
There are many, many ways! It's what groundwork addresses, first and foremost, as far as I'm concerned. I think your method is close to lunging-till-exhaustion? Trot until you feel a "ralaxation"? I'm not saying it won't work, as it's worked for you, but I'd prefer a horse that hasn't been brought down by fatigue.
I think much of our disagreement is in the level of relaxation: one doesn't expect to put your horse to sleep before mounting up. Nevertheless, I do see (and I've done this myself) where a rider wants to get on with it, but her horse is so upset he's not only completely inattentive, but dangerous. Nowadays, I try to avoid dangerous riding.
"Assumptions make an ass of you and me." - Quote from my 8th grade English teacher.
No, I don't run my horses down to get them to relax. Ride rhythmically and it relaxes the horse, as per the German scale. To ride rhythmically one does not have to go lap upon lap around the arena until the horse is exausted. One simply has to ride in balance and influence the balance of the horse until he is in a rhythm. This "system" or "pattern" naturally relaxes the horse because they are a creature of habit.
I also hate lunging horses. If they're broke, they shouldn't need to be lunged. Not only is it boring as watching paint dry, it's hard on their joints, tendons and ligaments. Not to mention my diziness center.
The point of dressage, in it's classical form, is not to teach the horse. It knows rhythm, it knows cadence, it knows all the Grand Prix already. The point is to train the horse to do these things with the added weight of the rider, and on the rider's aids. Whether it's Muffy out in the field on her 35 year old standardbred or a competetive dressage rider looking to the international arena, the goal of dressage is not to teach the horse anything but rather train him under a rider.