The Zohar discusses the creation of the sun and the moon, which originally were of equal size and importance. But the moon was not content, and she cast a jealous eye on her cosmic neighbor. As a result of her envy of the sun's illumination, the moon was eventually reduced in both size and significance. Henceforth, the moon would have no light of her own. Instead, she must reflect the light of the sun.
Here the Zohar reveals a profound secret of human nature. This is the origin of the trait known as Hatred For No Reason. Sometimes we are envious of our neighbors' possessions even if we possess exactly the same things. Instead of appreciating our lot in life, we begrudge the lot of others, even though it in no way diminishes our own.
In Kabbalah, the reduction of the moon symbolizes the separation between the male and female aspects of The Creator. This manifests as the separation of the spiritual dimension Zeir Anpin, or The Upper World, and the physical realm of Malchut, or the Lower World. Just as the moon's light is derived from the sun, Malchut's Light is drawn from the world of Zeir Anpin. Through positive deeds and actions and the removal of our jealous nature, we can unify these two dimensions and create a flow of Light into our lives. Reading this section gives us the ability to bring about this unity when we recite our prayers and perform the necessary spiritual actions.