Baal HaSulam, Preface to the Wisdom of Kabbalah, Item 25: Thus, as long as not all five Kelim KHB TM have grown in a Partzuf, the Lights are not in their designated places. Moreover, they are in inverse relation: in the absence of the Kli of Malchut, the Light of Yechida is absent, and when the two Kelim, TM, are missing, Yechida and Haya are absent there, etc. This is so because in the Kelim, the Higher ones emerge first, and in the Lights, the last ones are the first to enter.
The opposite order between Lights and vessels is very confusing. According to this order, the more we advance, the greater the darkness we enter. It is because we need thicker vessels in order to discover greater and stronger Lights. Therefore, I need greater support from the group and need to attend the lessons regularly, which means to sustain myself by greater powers than before.
Usually, the more I advance, the more I understand and feel, and the more I discover, but at the same time, I find myself in greater darkness since that’s the way it always is: greater Lights require thicker vessels.
You will also find that each new Light that reenters dresses only in the Kli of Keter. This is so because the receiver must receive in its purest Kli, the Kli of Keter.
For this reason, upon reception of each new Light, the Lights that are already dressed in the Partzuf must descend one degree from their place. For example, when the Light of Ruach enters, the Light of Nefesh must descend from the Kli of Keter to the Kli of Hochma…
We must make an additional effort in the vessel by the darkness that we discover and its correction. Thus, the vessel of Hochma is added to the vessel of Keter, and then the Light of Nefesh that was in the vessel of Keter descends to the vessel of Hochma and the Light of Ruach enters the vessel of Keter. The difference between the Light of Nefesh and the Light of Ruach is very large. It is a new world, a new attainment, a new feeling that never has been felt before.
The perception of reality is upgraded each time. Reality seems new and different. The upper force is revealed more in some new form, and the world, the general vessel, seems new. Every slight shock in the spiritual world summons a change in the whole integral system, and it is, therefore, very meaningful whether one is in Nefesh of Keter or in Ruach of Keter.
From the 3rd part of the Daily Kabbalah Lesson 3/23/14, Writing of Baal HaSulam