Night and day, are two extremes of our daily swing on life's complex pendulum. The day brings light, the night replaces the light with darkness. Together they guide the affairs of men, for if there ceases to be a balance between light and darkness, then existence as we know it would come to an end. Light needs darkness to remain useful, just as much darkness needs light.

Pendulum Series - Episode Four: The Lost.

http://www.pencillite.com/2017/08/pendulum-series-episode-four-lost.html?m=0