Byron Nelson did this prior to his breakout season of 1945. He had been keeping notes on his rounds in 1944 and came to the conclusion that there was nothing he needed to change in his golf swing. He realized that what he needed to change was his mental approach.
Byron realized that in almost every round he played there were relatively easy shots, especially on and around the greens, that he played, not necessarily wrecklessly, but without giving the shot his full attention. And because of this he was missing a makeable putt, or failing to get the ball up and down due to nothing more than lack of attention and focus.
Byron came to appreciate the truth of what Bobby Jones had written about; that the hardest shots to focus on were invariably the easiest looking ones. It's not hard to give a difficult shot your full attention. But those easy-looking chips and putts can get away from you when you take them for granted. And it really hurts your psyche when you waste shots. You can forgive yourself for missing a shot. We all miss them. But when you miss a shot because you were careless, it stings.
Lord Byron entered the 1945 season knowing that he wanted to make enough money to retire to a ranch and leave the grind of the tour. He wanted to try to establish a few records if he could during that process. And what he knew, most of all, was that he wasn't going to do it unless he played every shot for all it was worth. He couldn't afford to take any more mental holidays out on the course. And Byron vowed to do exactly that--to grind over every shot for an entire season.
Byron Nelson was already a great player. He was routinely beating guys like Hogan and Snead. And his ballstriking was almost monotonous in its efficiency. But when he added the determination to grind out every shot, he nit only played great golf; he played golf the likes if which had never been seen before. He won eleven tournaments in a row, and eighteen in a single season. His scoring average of 68.33 stood as the lowest scoring average ever until a certain Tiger Woods came along more than sixty years later.
All the great players were great because of their ability to focus and concentrate. There are lots of guys who can hit great golf shots and go low from time to time. But the great ones know the importance of playing golf one shot at a time. And they are able to actually do it.
I have played this game for over fifty years. I've played some half decent golf, and shot as low as sixty five. But I don't think I've ever come even close to playing an entire round of golf where I gave every shot my all--playing one shot at a time. Oh well, there's always next year.