戴尔·卡耐基/Dale Carnegie
Why am I writing a chapter on preventing fatigue in a book on preventing worry？That is simple：because fatigue often produces worry, or, at least, it makes you susceptible to worry. Any medical student will tell you that fatigue lowers physical resistance to the common cold and hundreds of other diseases and any psychiatrist will tell you that fatigue also lowers your resistance to the emotions of fear and worry.So preventing fatigue tends to prevent worry.
Did I say"tends to prevent worry"？That is putting it mildly. Dr.Edmund Jacobson goes much further.Dr.Jacob son has written two books on relaxation：Progressive Relaxation and You Must Relax, and as director of the University of Chicago Laboratory for Clinical Physiology, he has spent years conducting investigations in using relaxation as a method in medical practice.He declares that any nervous or emotional state"fails to exist in the presence of complete relaxation."That is another way of saying：You cannot continue to worry if you relax.
So, to prevent fatigue and worry, the first rule is：Rest often. Rest before you get tired.
Why is that so important？Because fatigue accumulate with astonishing rapidity. The United States Army has discovered by repeated tests that even young men-men toughened by years of Army training-can march better, and hold up longer, if they throw down their packs and rest ten minutes out of every hour.So the Army forces them to do just that.
Your heart is just as smart as the U. S.Army.Your heart pumps enough blood through your body every day to fill a railway tank car.It exerts enough energy every twenty-four hours to shovel twenty tons of coal on to a platform three feet high.It does this incredible amount of work for fifty, seventy, or maybe ninety years.How can it stand it？Dr.Walter B.Cannon, of the Harvard Medical School, explains it.He says："Most people have the idea that the heart is working all the time.As a matter of fact, there is a definite rest period after each contraction.When beating at a moderate rate of seventy pulses per minute, the heart is actually working only nine hours out of the twenty-four.In the aggregate its rest periods total a full fifteen hours per day."