Back when I shot bow-and-arrow, I practiced pretty regularly at a nice indoor range. The guy who sorta took me under his wing gave me similar advice about aiming (maybe he knew the story?). I found an interesting benefit to focusing only on the x-ring of the target. When I was at full-draw, there was nothing else going on anywhere in the world other than the 20 yards between my arrow tip and the little X. No problems, no hassles at work. When I was done practicing, I was quite relaxed.