One common trick is to have a "trigger" in your preshot routine - like putting the chalk down on the rail after you've walked around and done all the thinking - to signal to your brain that it's time to stop thinking and start performing.
pj
chgo
There’s a similar approach that is taught in golf where you have a ‘think box’ and then a ‘play box’. You do all your planning before you take your stance over the ball and that’s your message to stop thinking. Easier said than done.