Mark Avlon said:I agree that practice should be challenging, but not so difficult that it is unlikely that you can successfully accomplish the task. It is also important to know your limitations (margin of error).
Well designed progressive practice drills can provide both. They are great for improving skills and once you find the point where you're 50% successful, you will know what your chances are for success when shooting a given shot.
While practicing position on a dime provides a clear goal, whether you land on the dime or not should not be the measure of success. If it is, it will only lead to frustration. Instead, you should use this type of drill to determine you margin of error. You can then practice to reduce the margin of error.
Practice should be structured and goal oriented. Goals should be Specific, Measurable, Attainable, Realistic, and Timely (SMART). For example, "My goal is to develop the skills to stop the cue ball within the width of a ball in 1 month." You need to also identify what might keep you from attaining your goal. Do you know what must happen to cause the cue ball to stop? Are you mechanics accurate and consistent enough? Is your speed control accurate and consistent enough? If an answer is no, then you have to work on that piece of the puzzle in order to reach your goal.
I agree with Mark. Trying to stop "on a dime" is a good practice theory, but, should not be a situation whereas you frustrate yourself while trying to get the perfect position on a shot.
Making your position Attainable and Realistic is the key. Also, trying other position routes is a good idea. But, put that "other" route within a logical thought process.
When trying other position routes to get into tighter areas, pick a shot that brings you into the position zone instead of across it. See the diagram below.
If you make logical route choices when choosing these "other" routes, it will not only improve your position play, but, give you a goal that can be achieved.