Do you frequently get told to keep your hands still?
Yet you feel like your hands are still, and the all your attention is focused on keeping them motionless and your instructor still tells you that they are dancing around?
Off the horse, sit in a chair and hold your hands and arms in the correct position. Now stand up and sit down, as if you are rising to the trot. Can you see that when you are keeping your arms in that fixed position that your hands are going up and down. If not, ask someone to video you and then you can see the extent of movement for yourself.
Now, get a friend to hover their hand over your fists as you sit in the chair. When you stand you will feel your hands hit theirs. But they should resist the push. The next time, open your elbow as your stand up. Your fists shouldn`t hit your friend`s hand. As you sit down, close the elbow.
It`s almost as if your fists are pushing down on a button as you rise, and lifting off the button as your sit.
So the next time you`re riding, just trot large for a few minutes while you`re warming up, focusing on pushing the button, and flexing the elbow joints as you rise. You should feel that your hands stay stiller, but your arms are also more relaxed. Hopefully after focusing on this opening and closing it will become natural and when you move onto other exercises you should feel the improvement in the contact and the way your horse goes.