What will probably happen if a person can’t sleep well? If a person can’t sleep

It is obviously true that all of us need to sleep, but most people rarely know why and how they sleep.
    We know that if we sleep well, we feel rested. And if we don’t sleep well, we often feel tired and impatient. It seems there are two purposes of sleep: physical rest and emotional and psychological rest, through which we can rest our bodies and our minds.
    Every night we have two kinds of sleep: active sleep and passive sleep. The passive sleep gives our body the rest that’s needed and prepares us for active sleep, in which dreaming occurs. The brain rests, then it becomes active, then dreaming occurs. This cycle is repeated several times throughout the night. During eight hours of sleep, people dream for a total of One and half hours on the average.