The Upper One is only waiting for a reaction from us. Portions of Light come from the Upper One to the lower one (to every one of us), demanding the right reaction from us in response. The Upper One knows exactly what is happening to the lower one and what state the lower one is in because He forms this state for the lower one.
Of course, the Upper One knows what the lower one is ready to do. He arranged all of the external and inner conditions for the lower one to ensure him free choice, leaving the lower one just one thing that is unclear and unknown to the lower one – the middle third of Tifferet (Klipat Noga). Precisely in this state the lower one has to form the middle line on his own.
If in response to the Upper One’s influence, the lower one correctly builds the middle line, this means he becomes worthy. Then he really shifts himself and the whole world (all of the environment that the Upper One has formed for him at this moment) toward good.
Therefore, the only thing required of the lower one when he feels a lack (Hissaron) is to turn to the Upper One in order to receive the component he lacks in order to shift himself and the whole world to good. The lower one lacks knowledge, sensation, and later the ability to make a decision. He must receive all of this from the Upper One.
The Upper One leaves the lower one Klipat Noga in order for him to desire to turn to Him and receive what he lacks. If the lower one is ready to receive this supplement for Klipat Noga, then he receives it. This is the additional force of bestowal that he acquires on the current degree, which enables him to rise to the next level.
From the 1st part of the Daily Kabbalah Lesson 12/13/10, The Zohar