The old adage that "over-analysis leads to paralysis" is often true in the game of pool. One of the primary difficulties pool players face is the amount of time they have as they transition from one shot to the next. In reality, this is both an advantage and a problem.
The advantage is you don't have to shoot the cue ball until you are completely ready. The problem is this extra time available can be completely misused. When you use that extra time to over-analyze a shot then your brain can become frozen and send the wrong signals to your body. The mind can only process a limited amount of information at one time.