[1.III.6.6] Reinforcing the Memory
One of the most useful memory devices is reinforcement. A forgotten memory, when regained, is always better remembered. Many people fret that they forget. Most people need to forget and re-memorize three or four times before anything is permanently memorized. In order to eliminate the frustrations from forgetting and to reinforce memory, try to purposely forget, for example, by not playing a piece for a week or more and then re-learning it. Or quit before you completely memorize so you must start all over again the next time. Or instead of repeating short sections (the method you used initially to memorize the piece), play the entire piece, only once a day, or several times a day but several hours apart. Find out ways of making you forget (like memorizing many things at once); try to create artificial blackouts -- stop in the middle of a phrase and try to restart.
Memorizing new material tends to make you forget whatever you had memorized previously. Therefore, spending a lot of time memorizing a small section is not efficient. If you choose just the right number of things to memorize, you can use one to control the "forgetting" of the other so that you can re-memorize it for better retention. This is an example of how experienced memorizers can fine-tune their memorizing routines.