I agree with everyone suggesting the SLOW WORK! It can be repetitive and boring but it makes the world of difference when it is time for you and your horse to go out and compete. This is a personal thing, but when I choose a few things to accomplish slow I refuse to move on until those few steps, cues etc are accomplished and are perfect. If my horse goes into her pocket and decides not to sit down and rate or pick her shoulder up I will NOT move on until we have a common understanding. It's really hard, but if you are up for the challenge it will payoff great in the end result!
**If you aren't terrified then you are not running fast enough**