DARKNESS IS IMPORTANT TO RECUPERATIVE SLEEP.  In order to get the highest quality sleep, you need to be in a room that is dark as possible. Even the slightest bit of light can disrupt your body’s circadian rhythm and production of melatonin and serotonin, two hormones vital to your health. Many people are not aware that exposure to the smallest amount of light at night will cause your body to halt production of those hormones. Exposure to light while your body is trying to sleep activates your stress response and weakens your immune system, which is why irregular sleep cycles can lead to stress-related disorders. Many of your major organs and body systems have their own internal clocks. These clocks influence everything from your body temperature to hormone production to your heart rate. When these clocks are out of whack, all kinds of things can happen which impact your daily life and your overall health. See these links for tips on getting good sleep naturally:  

Our ancestors used to sleep twice a night
The secret to rest is staying in bed in the dark with eyes closed
Restful sleep and increasing melatonin levels naturally
My sleep habits are morphing again
I may not need to change my life, I may just need to change my perception of it
The morphing sleep cycles of menopause; 15 things to do when you can’t sleep
Not able to sleep? Turn Off The TV, Turn Off The Lights
Melatonin 101