To avoid overriding your horse...
Use your aids only when you feel the horse is beginning to disrespect them. You can compare this to a kick-sled—when it has picked up the desired speed, you stop pushing it and only push it again when it starts to slow down.—Kyra Kyrklund
Kyra Kyrklund represented Finland at the 1990, 1994, 1998 and 2006 World Equestrian Games. This solution originally appeared in her book, Dressage