Sometimes memory is weakened by too great a strain put upon it. When one tries to remember, this puts a strain upon a process which is natural. It is the nature of memory to remember, but when you put a strain upon it: "You must remember!", then it will forget. The very fact that you have strained it will make it forget. One must not try to impress one's mind more deeply than it naturally becomes impressed. One's attention is quite enough. Will-power must not be used to remember things; it is a wrong method that people are applying at present when they say that in order to remember things one must will it. By willing one weakens the memory. Besides this, a balance between activity and repose is necessary.