On the putting green the diameter of the hole will never change. However the speed in which you hit the putt and the amount of break you allow will make a difference to whether the ball finds the bottom of the cup.      A great way to practice is to place a tee in the back of the cup and use this as your target. With the smaller target your aim will improve and although you may miss the exact point of the tee the ball will still find the bottom of the cup. You can also move the tee to the right side of the cup for a breaking right-to-left putt and to the left side for a left-to-right breaking putt. Pin pointing your target will help to hole more putts and lower your score.