Baal HaSulam, Beit Shaar HaKavanot (The Gatehouse of Intentions): “The Moon waned on the fourth day of creation, for in the beginning Zeir Anpin and Nukvah were as two great lights, standing on the same degree, back to back, and Nukvah had a full spiritual Partzuf of ten Sefirot of the reverse side. [This means Nukvah contained spiritual vessels. Why, then, did she lack lights?] When the Moon made a complaint, saying that two kings cannot use the same crown (Keter), she was told, ‘Go and diminish yourself!’ Thus, she returned to a point beneath Yesod of Zeir Anpin, where she dwelled prior.
Malchut (creation) thought that she could be the same as Zeir Anpin; however, she could not shine as he. She ascended to Bina in order to receive Light like Zeir Anpin, but was unable to. This was for the reason that Zeir Anpin possesses the quality of bestowal. His nature is the Light of Hassadim and He feels perfection even when there is no Light of Hochma. He shines with the Light of Hochma anytime he wishes so because he always has the Light of Hassadim.
However, Malchut does not have the Light of Hassadim and she feels her existence in the Light of Hochma as darkness. This constitutes the complaint made by creation (Kitrug Yareach): “I can ascend to the height of the very World of Infinity, but if I don’t have the Light of Hassadim, the Light of Bestowal, then the Light of Hochma won’t shine for me and I will only feel greater darkness.”
When do we reveal that we are in the dark? It’s precisely at the time when we are being elevated! When we are slightly elevated upward, it makes us feel that we lack the corrected desires, the Light of Hassadim. This is what we perceive as darkness.
We don’t feel darkness because we fall, but because we ascend; however, it’s because we ascend without the garment of the Light of Hassadim, the Light of love and bestowal. What we consider descent is actually the ascent, but one that is not corrected. Likewise, what seems to us as an ascent is really a descent, because we receive what we are given into the desires of reception. Thus, everything is the other way around in the spiritual world.
From the 2nd part of the Daily Kabbalah Lesson 4/7/10, Beit Shaar HaKavanot