Everyone knows you must exercise regularly to keep good health. Indeed, staying physically fit is a big part of our culture, we consider (or rightly so) that healthy people are attractive people. Since most of us want to be attractive, there is no shortage of exercise clubs, training videos, magazines and books offering to help us stay physically fit. Unfortunately, however, our culture doesn’t place the same emphasis ( 重视 ) on mental fitness. Although we tend to like men and women with strong, healthy-looking bodies, we don’t have the same degree of respect or attraction for smart, educated, mentally healthy people. This is a pity, because there are great rewards for people who have developed the ability to think well. If your mind is well trained and flexible ( 灵活的 ), you will be able to understand a great deal of what happens around you. And if you are also well educated—that is, if you understand basic science, mathematics, music, art, literature, history and so on—you will find it much easier to make good decisions throughout your life. Over the long run, this leads to a sense of control over your destiny ( 命运 ) and a much better life than otherwise (in another way). People who are poorly educated or who don’t think well—that is, people who are not mentally fit—see things differently. Their world is controlled by mysterious, often malevolent ( 恶意的 ) forces. Such people live within a system they will never master, forced to follow rules they will never understand. Although it may not be obvious, most spend their lives being manipulated ( 控制 ) by others. They are told what to do, what to think, how to spend their money, and what they should and should not aspire ( 渴望 ) to in life. In my opinion, if you want to live well, you must be able to use your mind well. For this reason, I want you to be able to concentrate, to solve problems, to understand complex ideas, and to think clearly and quickly. Such skills will make it easier for you to make informed decisions, understand current events, choose good friends, manage your money well, make wise long-term decisions and appreciate music, art and literature. The key to developing such skills is to enjoy learning, and to have the ability and motivation to teach yourself.