If you are feeling down, you might try counting the stars

Your eyes have specialized light receptors which relay your surrounding light level to a gland in a brain call pineal gland

In the darkness, the pineal gland produces Melatonin, a hormone that cause drowsiness in your body. Daylight inhibits the secretion of Melatonin.

By lifting your field of vision to high level your body is able to live your mood.