Classical Training: The Art of Letting Go
The following article is by Sarah Warne with quotes by Nuno Oliveira. It appeared on the web site www.eurodressage.com. I want to thank Angelika Gruber of Ocala Florida for bringing it to my attention.
There is a huge difference between a firm and effective rider, and a firm and forceful rider. The difference lies in the art of letting go: knowing when to release the pressure, soften the reins, relax the legs. The art of knowing when to say "thank you" and these thank yous must be obvious.

When the horse relaxes really give the reins and make it really clear that his relaxation corresponds with the total relaxation of yourself as a rider.
"Make it a habit to praise when the horse yields." N. Oliveira (1998)
When the horse "yields" always remember it is better to reward too much than not enough. If you don't make the reward clear to the horse you risk confusing him as to what you want and next time he will be reluctant to soften or will simply not soften at all.
"It is always better to risk losing the contact a little, than not to yield at all." N. Oliveira (1998)
A firm yet effective rider will demand consistency and submission, but will achieve this long term by telling the horse clearly when he has done the right thing. Yet the hard part is that even the best trainer in the world can't tell you exactly when to soften. They can tell you when you should have softenend, but as riders we must learn to feel the split second the horse relaxes through his body and accepts what the rider is asking.
"The hands have to be like consrete when the horse resists and like butter when he yields." ..."Don't play the master all the time. The difficulty is to feel to what extent one has to intervene." ..."When a horse gets nervous during a new exercise, one has to calm him down during the exercise. Otherwise he will get nervous every time we ask something more or something new from him" N. Oliveira (1998)