Sleep is the largest overlooked part of your life and a vital part of happiness.
— David K. Randall, Dreamland

The infographic to the right states what happens to our bodies during the five stages of sleep.  The most important sleep that we get is REM sleep, which takes up a quarter of our night.  REM sleep provides energy to our brain and body for performance - in order to be successful during the day, you need good REM sleep at night.  Our levels of cortisol, a hormone essential to maintaining balance in our bodies, decrease during bed time and increase when we snooze to aid us for day time activities. 

Sleep and health have a bidirectional relationship: “poor sleep compromises health and poor health disrupts sleep.”  Most people are unaware of how beneficial sleeping actually is for our bodies.  A sleep deprived brain acts like a brain under the influence of alcohol.  Lack of sleep impairs your prefrontal cortex, the brain region that is less active than usual after sleep deprivation.  Many brain areas are down-regulated when there is absence of sleep including dulled senses, loss of creativity and lateral thinking, disruption of new learning, and a negative mood.  It also affects your ability to concentrate, judge, make decisions and retain memory.  Sleep deprivation increases irritability, anxiety, depression, and the risk for major health issues, including cancer and heart disease.  After noon on a workday, it’s a myth that lunch is the cause of drowsiness, but it’s actually the disruption of circadian rhythms.  These rhythms play a huge part in sleep patterns.  Lapses of attention span, impaired working memory, and impaired procedural and declarative learning are all symptoms of a slight change in circadian rhythms.  Scientists are just discovering what happens to the brain during sleep.