If you do not use your arms or your legs for some time, they become weak; when you start using them again, they slowly become strong again. Everybody knows this. Yet there are many people who do not seem to know that the memory works in the same way. When someone says that he has a good memory, he really means that he keeps his memory in practice by exercising it regularly, either consciously or unconsciously. When someone else says that his memory is poor, he really means that he does not give it enough opportunity to become strong. The position is exactly the same as that of two people, one of whom exercises his arms and legs by playing different kinds of sports, while the other sits in a chair all day. Not all of us can become extremely strong or clever but if we want to, we can improve our strength and our memory by the same means - practice. Have you ever noticed that people who can not read or write have better memories than those who can? Why? Of course, because those who cannot read or write have to remember things, dates, times, prices, names, etc., that they can not write down. So their memory is always being exercised.