Another important reason for the darkness is the fact that it stimulates the production of melatonin hormone in your body. Production of melatonin by the pineal gland is inhibited by light and permitted by darkness. Melatonin regulates sleep patterns and amount of Leptin hormone. The melatonin signal forms part of the system that regulates the circadian cycle by chemically causing drowsiness and lowering the body temperature.

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My Demon revokes any prayer
He's grown contempt for love and hope
He betrays trust, twists truth and fair
Indifference is his way to cope
Engulfing sound of sensations
He quells with voices of despair
And muse of short lived inspirations
Flees at the sight of his cold stare
~Moy Demon - Mihayeel Lermontov~