I was told to stop playing games of pool with opponents completely and only shoot this drill while working on correcting about ten fundamental errors. (elbow moving, shoulder moving, head raising, moving grip hand back...etc) I stopped playing my friends and gambling and did nothing but this drill for several months and it was the best thing I've ever done. I did it for about two hours a day, and for the first few weeks everyone was harassing me about not playing and making fun of me.
I got to where I could make a hundred in a row stopping the cueball, then I progressed to drawing back a diamond and punching the cueball forward a diamond and so on. Some days the connection to my stroke and my focus and presence in the moment was so magical I felt like I had learned the secret to pool and would never miss again. I went from being a slightly above average player at the beginning to suddenly winning every tournament I entered and right after that I won over $7,000 in one month.
For anyone who has the passion to improve their game I believe there is no faster way to create a perfect stroke than this method. When I wasn't on the table doing this drill I was in front of a mirror doing it until I couldn't lift my cue anymore. There are no shortcuts to a repeatable stroke. I believe in this intense, muscle destroying, endurance testing way. For those of us who have been playing for years with fundamental errors they will always pop back up under pressure unless we retrain our stroking arm that intensely and in that short of a time frame.
After a few weeks of thousands of the same shot you will discover the magic and pleasure of focus and the joy of an almost spiritual awareness of all aspects of your stroke. You'll find yourself in the zone on a weekly basis instead of once a year.
I'm sure people will disagree strongly and say that many different drills, gambling and working on all aspects of your game through competition with better opponents works. No. Not when it comes to fixing errors in your stroke. And without a fundamentally solid stroke all the other practice is built on weak foundation.