True Way

The true way so that it remains is to understand, it is not to learn by heart. You learn something by heart, it is mechanical, you see; but after some time it will be effaced, unless you make use of it constantly. For example, you are made to learn by heart the multiplication tables; if you constantly use them, you will remember them, but if by chance for years you remain without using them, you will forget them completely. But if you understand the principle, you will be able to remember them.

Ref: Questions and Answers 1955