OK, this post is probably going to run a little long or a lot long, three more or less separate things:
As Greg and others have mentioned. Think standing. If you can't quit thinking or are uncomfortable with the shot, stand up! If your mind absolutely will not quieten in the down position, think one word related to the shot or a very short phrase. My mantra is "smooth" whether I am shooting pool or five steel plates in just over two seconds. I use it for almost any activity.
On to my pet peeve, keep thinking three shots ahead! Nope, don't do it. That means that you have to think after every shot and I am trying to make the entire inning one continuous action. It can't be if I have to stand up and add a ball after every shot. I plan my path to a safety or past the money ball every inning. Notice I said past the money ball. I know where the cue ball is going on the money ball shot too and I planned it at the beginning of the inning. Call that information a freebie, one more thing left to talk about.
Information. Information is a valuable commodity. Watch the other player carefully for any information large or small they might give away. Try to give away as little as possible yourself. You know where you want the cue ball after the shot, locking your eyes there a second or two can drive that home if you feel the need. Point the cue at that spot and you just announced the spot to the world and everyone including your opponent can evaluate how well you are shooting. We can give out false tells and I sometimes did, especially indicating shots I didn't like. I was like Br'er Rabbit, "please don't throw me in that briar patch!" Usually wasted effort, a lot of other things to focus on.
A piece of candy to close with, most players shoot too hard most of the time! As the Eagles sang, take it easy!
Hu