Man still has a lot to learn about the most powerful and complex part of his body -- the brain. It may be surprising to learn that it isn't age that makes you lose your memory. The reason could be that you have a "lazy" memory, not an old one. Like your body your memory improves with exercise. Once given plenty of exercise, the brain keeps its power. Before discussing how to improve the memory, let's look at how the brain works. There are two sides to the brain, the left and the right. The right side deals with the senses (what we see, hear, feel and smell). It's the creative and imaginative side. The left side is concerned with logic. It analyzes information and puts it in order. Some recent research suggests that we remember everything that happens to us. The problem most of us has is recalling events. Most forgetting takes place immediately after learning. An hour after learning something new, more than 50% has been forgotten. After a month, 80% has been forgotten, and so on. This shows revision is very important. If you revise new material you have learnt, you remember much more. So it's of vital importance to revise newly learned material often, and have frequent breaks. We best remember what we learn at the beginning of a learning period and at the point where we stop. After the break, revise what was learned before the break and then continue learning the new material. These breaks should happen every 20 or 45 minutes. Other experiments have shown the brain needs time to "digest" what has been learned. The time necessary for this is 5 to 10 minutes. After the break, the memory will have absorbed what it has just learned, and more will be remembered. During this period it is important to exercise the right side of the brain, because the left side is used during the learning period. Therefore you should relax. Listening to music, breathing in fresh air, and looking at a picture are all ways of using the other side of the brain. So when you are studying alone, make a plan which shows when to have breaks and to revise newly learned material immediately before you begin studying again. If you do in this way, your memory will improve. According to the text, you lose your memory by   _  .
getting too old hardly using your brain working too hard using your brain too much