When you wake up in the morning and you feel energetic and refreshed,ready to jump out of bed and maintain this feeling for the rest of the day.You may have slept 9,8 or only 7 hours,each one of us needs a different amount of time in bed to feel good.

And if you did sleep enough time but feel tired and sluggish you may have one or more of the common sleep disorders like Sleep apnea, obstructive or central, Periodic leg movements of sleep, REM sleep behavior disorder or less common like narcolepsy and idiopatic hypersomnia.

If you have a hard time to fall asleep or you wake up frequently and can not fall back a sleep you have insomnia, a very common problem that can be very disrupting and sometimes difiicult to contoll.

Please see this link from the National Sleep Foundation for sleep quotes(PDF fie).

See also How sleep works.

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Please do not forget to find out how sleepy you are.