The most difficult thing (in any game/sport) is to hit the ball EXACTLY in the center, with no spin or deflection...pool's the same because if you just hit the ball minutely off it will deflect in the opposite direction...because the very best players realize this (either consciously or unconsciously) they will intentionally hit the cue ball to one side or the other (except when slow rolling a shot or on shots straight in)....that way they know FOR SURE which way the ball will deflect and if they hit it off center a bit more it will deflect a hair more, but most importantly if they hit it off the OTHER WAY it will just not deflect AT ALL.....the worse thing you can do is to try to hit the center every time and slightly hit it off one way OR THE OTHER...this way you will NEVER know why you are missing (and often leads to "fixing" the wrong thing).....and when you do you will often UNDERCUT shots...this is the worse mistake you can make.....if you notice, when a champion player misses they almost always OVER-CUT the shot...this is no accident, when I miss a shot I will always know it was from something tangible, not that I "MAY Have" hit the wrong side of center and "accidently" veered the ball the wrong way.