As the worlds expand from above downward, every Partzuf is smaller than the Partzuf that preceded it, like its another try to utilize itself on a lower level. Suppose that on the lower part of the Partzuf of Galgalta I cannot receive a steak for the sake of bestowal, but I can receive fish. This attempt to add something else is called Partzuf AB.
In the lower part of Partzuf AB I cannot receive fish, but I can receive a salad, and this is called Partzuf SAG. Each time I have another opportunity to add on a lower level than before. Thus the path back from below upward is prepared for us, on which we rise from this world to the world of Infinity, by adding on each level.
You rise since with your Galgalta ve Eynaim (GE) of the lower one, you can add something to the AHP of the upper one. Although it may seem to you that you cannot add anything to it—after all, the AHP of the upper one is very big compared to you and you only annul yourself in it, like an embryo in relation to his mother—by that you add the state of greatness (Gadlut) to the upper one. Without you, it could never become great.
Although you exist as a vegetable there, by totally annulling your personality, you are enabling the upper one to be great on its upper level.
From the 3rd part of the Daily Kabbalah Lesson 3/8/2012, TES