What are the top 3 reasons why a good night’s sleep is essential? Sleep is important for your immune system to function properly. Your cells renew and regenerate when you sleep. Eight hours a night is necessary in order to have a health immune system. Another reason why a good night sleep is important is to look fresh on the outside. Dark circles and bags and dull skin will result if you do not have a proper rest. If you want healthy glowing skin, a good night sleep is essential. Another reason is to keep a happy spirit. When you are tired, you are more likely to be irritable. When you are irritable, you will draw more experiences that are irritating your way. It is a vicious cycle.