To achieve perfect impact on short-game shots, it's all about lag. Should the clubhead lag behind your hands into impact, or should your hands lag behind the clubhead? It depends on whether you need a powerful shot or a soft touch.
Sometimes simply willing oneself to stay still doesn't get the job done. When that's happened to me, I've often solved the problem by making a conscious effort to set my weight on the insides of my feet or on the balls of my feet.