In total darkness it is difficult to see where you are going.  Darkness usually frightens people.  they can't see where they are going; they might not know what lurks in the shadows.  There is also spiritual darkness: doubt, losing joy or the experience of closeness to God.  St. John of the Cross called this spiritual loneliness the "dark night of the soul."  There is only one way out of the darkness.  Like miners in a cave who kept candles lit to light their way, you need spiritual light to light your way.  find out how.