Concentration is the root of golf mastery. It is much more than the ability of not being distracted or even visualizing the golf shot.
Granted, hardly any of the authors of ANY golf training book have comprehensive training in golf psychology, so let me give you some tips for peak concentration on the golf course. I'm not talking about "grinding" out on the golf course...this will burn you out early in the round and mentally deplete you.
First off, dance with which you brought to the course...in other words, don't try to fix your golf swing out on the course. There is plenty of time to fix your swing on the range after the round. Your job on the course is to play golf, not play swing...you need to score!
Your thoughts need to be focused on getting the golf ball into the cup in the least amount of strokes possible...the object of the game! (How soon we forget this fact) The only things you should be thinking about while you plan your golf shot is the target, distance, direction, wind speed, your lie...and any other factor that comes into play.
Forget about your last shot and what score you might shoot. Only concentrate on the golf shot at hand. You must discipline yourself to stay in the moment...this takes time to master...if you want to become an accomplished golfer you will master this skill.
Once upon a time your ability to concentrate was incredible. Before you could think or understand what words are. This was when you were a baby. Your brain was a sponge. As a baby you could hold your attention on anything in your field of vision without any distracting thoughts.
As you got older and learned how to talk and to think you soon became aware of that little voice inside your head that seems to be with you during every waking moment. It is that little voice that you can't quiet no matter how hard you try. It is always telling you that the golf shot is too hard, or that other golfer is better than you.