A man forgets because he does not concentrate his mind on his purpose, especially at the moment he conceives it. We remember only that which makes a deep impression, hence we must first deepen our impressions by associating in our minds certain ideas that are related to them.
We will say a wife gives her husband a letter to mail. He does not think about it, but automatically puts it in his pocket and forgets all about it. When the letter was given to him had he said to himself, "I will mail this letter. The box is at the next corner and when I pass it I must drop this letter," it would have enabled him to recall the letter the instant he reached the mail box.
The same rule holds good in regard to more important things. For example, if you are instructed to drop in and see Mr. Smith while out to luncheon today, you will not forget it, if, at the moment the instruction is given, you say to yourself something similar to the following:
"When I get to the corner of Blank street, on my way to luncheon, I shall turn to the right and call on Mr. Smith." In this way the impression is made, the connection established and the sight of the associated object recalls the errand.
The important thing to do is to deepen the impression at the very moment it enters your mind. This is made possible, not only by concentrating the mind upon the idea itself, but by surrounding it with all possible association of ideas, so that each one will reinforce the others.
The mind is governed by laws of association, such as the law that ideas which enter the mind at the same time emerge at the same time, one assisting in recalling the others.
The reason why people cannot remember what they want to is that they have not concentrated their minds sufficiently on their purpose at the moment when it was formed.
You can train yourself to remember in this way by the concentration of the attention on your purpose, in accordance with the laws of association.
When once you form this habit, the attention is easily centered and the memory easily trained. Then your memory, instead of failing you at crucial moments, becomes a valuable asset in your every-day work.