Rest is one of the basic human needs. Rest can be idle while to calm down and mind, or entertain ourselves. However the best rest for your body is get sleep enough. During sleep the body's hormones work optimally repair damaged cells. Besides the mind becomes calm.
If you lack sleep, it would be quite an effect on your health and stamina. Even lack of sleep can lead to reduced power of concentration, endurance to affect your life. It is therefore important for you to have a good sleep.
American Cancer society has been doing research on American citizens between the ages of 30-60 years. Research shows that people who have time to sleep 8 hours a day have a 12% risk of dying sooner, the risk increased to 17% in people who sleep less than 7 hours. Increasing the risk again if you sleep more than 9 hours which is about 34%.
Lack of sleep may increase the risk of early death, but excess sleep can also lead to premature aging and even the researchers stated that excess sleep can cause immune to viruses and tumors reduced.
Recommended that you sleep well according to your feelings. If you are sleeping 5/6 hours is quite refreshing then that would be enough, since sleep each person differently according to age.
Good sleep is a deep sleep or mutilated since that time the hormones work optimally. Other than that you should not sleep in a state of satiety or hunger.