I was not able to shake my cold to post this last week, but wanted to still touch on R' Tzadok haKohein's opening pieces in his sefer Dover Tzadek, and as IY"H we will see, they relate to these past few parshiyos. I have not learned Tanya in a long time, but I recall much of these same ideas can be found there. R' Tzadok starts with a gemara in Eiruvin(2) - "Mishkan ikrei Mikdash, u'Mikdash ikrei Mishkan" - the terms Mikdash and Mishkan are synonomous, and therefore halachic limudim can be made one to the other (we will not explore the halachic details here). R' Tzadok quotes that this gemara represents the idea of "Lshem yichud Kudsha Brich Hu u'shechintei", which according to chassidic tradition is said before performance of a mitzva.
Mishkan comes from the root Sh-K-N, to dwell. The Torah teaches G-d dwells within each of us because during creation G-d "blew" from his spirit into man, meaning inside every single person, even a Jew (and for the sake of simplicity we will discuss Jewish neshomos only) on the lowest level far removed from Yiddishkeit, there is a spark of neshoma which is a direct manifestation of G-dliness. In the guise of Shechina, G-d's presence hides itself in our world, hides itself in man, it masks its presence so that at times we loose sight of the fact that He is always with us.
At the same time, it is fundemental that G-d has no boundry, cannot be contained, cannot be delimited, and has absolutely no form. Mikdash comes from the root K-D-Sh, meaning separate (something which is kadosh is separate). Seforim refer to this aspect of G-dliness as the "ohr ain sof", the unbounded light of G-d, G-d in the most transcendent form we can conceive of.
The problem is if G-d has no boundry or container, we should cease to exist as independent creatures with free will (bechira) and just be subsumed under the "ohr ain sof", the infinity of G-d. G-d as Mikdash seems incompatable with G-d as Mishkan!
Without the illusion of our having a separate existance, there would be no concept of "malchus", Kingship, because a King by definition is a ruler over a separate domain. G-d is perfect, and embodies this trait of King as well. Therefore, through a process that we cannot even begin to understand, G-d created a "void" in which he created our universe and world that appears distinct and separate from Himself so that this idea of Malchus, G-d as King, can be revealed. This is the essence of the idea of tzimtzum, G-d "contracting" his presence to create the world. If a single word, the entire purpose of creation is Malchus.
The paradox is that even though there is tzimtzum and G-d is immanent and part of every aspect of our lives, we still believe G-d NEVER changed in TIME or SPACE from the unbounded "ohr ain sof" that has always and will always exist. Tzimtzum is not an event, because an event takes place in space/time and G-d transcends space/time - it is a concept, but exactly how this exactly works is beyond our conception in human terms. Mishkan, G-d as "m'tzumtam", contracted in the world and us, is always simultaneously Mikdash, the same transcendent boundry-less existance.
This is the idea of "L'Shem Yichud Kudsha Brich Hu U'Shechintei". We have to embrace K- Brich Hu, the transcendent, Mikdash, as one with Shechintei, G-d as immanent, as Mishkan.