It's all a mental game.
That's what I figured after long talks with one of the top players at my local place. I was fortunate he took an interest in my revisiting the game after so long and very fortunate that he was coming up to me to play a few racks. I 've heard since he is picky about who he plays.
He has been playing a long long time at a high level and often explains some of his thoughts regarding mental preparation, named a few books to read etc.
also watched this video which goes into the mental aspect and it gets interesting when he starts to talk about the conscious and subconscious part of playing the game. There are times I over think the shot, especially when running a table and get to a pretty straight forward black and miss it. I've realized my hole shot process changes when I start to over think, get nervous. I let the conscious part of my brain take over when I should simply allow my subconscious part, which knows exactly what to do, just get on with it and pot the fecking ball.
It's well worth a watch.