The key to pool is not "if you focus," but what you focus on. The less things the better, that's why it's important to find a way to free up your mind. The less calculations and judgments you have to make the better. Especially over the course of several hours if you are including choices that shouldn't even be considered it wears on your mind.
There are three things to consider on each shot after you know the situation. These are "the Angle you need to create," "where you need to contact the cue ball," and the speed needed to accomplish the shot.
From my experience it's best to "Blend" all these calculations into ONE THOUGHT PROCESS. This is something I believe my TOI technique does very effectively. In a short match it may not make a difference, however in long grueling matches or tournaments it may make all the difference. 'The Game is the Teacher" www.cjwiley.com
Thanks CJ, i partially agree with what you saying if you playing on large table pockets, once pocket size becomes very tight all what you saying changes.