We sometimes heard that life depends on exercise. It is true that exercise is important to our health, but in reality, it is not entirely so. The reason is that without exercise we can still live. However, if we have no sleep, we cannot live our life. Therefore, we must say that life depends on sleep.
Everybody knows that a baby grows by sleep. A new born baby needs to sleep twenty hours a day. An infant can sleep under any conditions, anytime, anywhere.
A human, except in the infanthood, has a life of three stages, youth, middle age, old age. At these three stages, sleep time will be decided by ourselves individually. We may sleep less or more which is entirely to depend on what we like to do.
For young people, sleep may not be so serous. They can fall into sleep quickly as soon as they lie down on bed. But, most young people like to devote their sleeping hours to I-phone, thus making themselves bad health as a consequence.
For middle aged men, many of them like to take their sleeping hours into playing, drinking, gambling or anything else. As a result, they will suffer illness of different kind which will cause their painfulness all their life.
Old people are better. As they have no energy to fool around they are forced to lie on bed. But, what they face is that they cannot fall into sleep due to their old age.