Wow, what strong words? But that is really the best and simple advise I have even been given to improve my putting. I would also be willing to bet it will work for you too.
Here is the full tip with proper explanation.
One of the most common putting problems amongst many amateurs is body motion during the stroke, which leads to unwanted power and inconsistency. Most golfers have no idea they are moving their bodies on the back swing, the through swing, or both.
When the putter goes back, the instinctive reaction of the head and upper body is to move forward; when the putter swings forward, the head and upper body rotate backward. This reaction may feel natural, but that doesn’t mean it’s good. In fact, it’s very destructive, as it affects the putter’s power and consistency through impact.
You must keep your head still. Don’t worry about holing any putts, just make good strokes without moving your shadow. Also resist the temptation to look at your putts after you hit the ball. Remember, putting is about accuracy, precision, delicate feel, and touch. By keeping your head still, you’ll promote good feel and touch, and become a better, and more consistent putter.
This seems almost too simple, but it works! Try it for the next 18 holes you play and let me know if you do not shave a few stokes off your score on your next round.