Ever notice how relaxed and loose Efren Reyes seems to be when he plays? That is one of the characteristics of his exceptional level of play. He usually has a laugh or a smile when he misses a silly shot. This is a key concept that is often missed. In any sport one's body must be relaxed and ready get it all together as needed. You can see this loose body in basketball at the free throw line when the player seems to shake themselves loose before attempting the shot. This is the precursor to enhanced focus: Let it all go so I can place all of my attention at one point.
Focus can be described as narrowing ones attention by excluding irrelevant information. It can begin by attempting to visualize the line of travel for the object ball from about six inches behind the OB to the pocket (see Jack Nicklaus' comments on visualization). This line is then visually traced to the contact point and one attempts to visualize the smallest possible contact point throughout the time the player is bending over. This will help exclude other information and one's focus increases with attention to physical detail that is real and imagined.
Focus often shifts to stroke mechanics for some people and this is perhaps disruptive. To the extent that one can learn to trust their mechanics and never lose sight of the place the cue ball is targeted focus increases and the body stays relaxed. It is for this reason that planning the cue ball's resulting position is done before one bends over. Once you bend over it is all about narrowing one's attention to exact lines of travel.
Basketball players, excellent golfers and pool players are not thinking about mechanics as they make a shot. They are simply looking at or concentrating on the ball. One of the things that helps one's concntration is knowing there is no aftermath from the resulting shot. Exceptional players simply walk away, shake it off, perhaps laugh and move to the next condition. When the unconscious knows there will be no self criticism following the shot it can concentrate all the more on the shot. Some people might be angry they missed but they are not angry with their self. Jimmy Connors comes to mind here as do some of the well known pool players. Anticipation of self recriminations can also effect one's play.