The sun must give its light to the moon, otherwise the moon would have no light. Dear Lord Jesus, my heart is Your moon; without You, it has no comfort. As the moon has more light at certain times and less at others, so is it with our heart: “The sweet hours of consolation come but seldom, nor do they last for long.” One moment we have a whole heart full of the light of comfort; and quicker than the flick of a wrist, all is extinguished. Oh dearest Lord Jesus, shine upon the full moon of my heart, lest in the night of temporal death my courage should wane and I despair.
[Herberger actually has several pages about how the sun illustrates Jesus. This is just the first of his ideas.]
Herberger, Valerius The Great Works of God: Parts One and Two: The Mysteries of Christ in the Book of Genesis, Chapters 1-15 88