Every single Dressage test requires the rider to change the horse's bend from one side to the other. With some tests having as many as 20 different opportunities to show the judge how good you are at changing your horse's bend. Or maybe how not so good you are at it!
For the horse, the learning happens on the release of the aid. That means if you don't release the aid, the horse will not learn.
"Don't take the tempo down without revving the engine." ~ Chris Bartle
I don't even think about aiming a young or green horse at a jump until I have them 100% in front of my leg on the flat. If you do, and the horse thinks about stopping, you will have no recourse, and will end up teaching him that
From Facebook fan Joan Dunlap ~ "Fix your position first... then the horse will adjust theirs."