Derived from Likutei Amarim/Tanya Perek 34. The perek opens talking about the fact that the Avos were on such a level of avodas Hashem that they were the Merkavah (Chariot) for the Shechinah. Variations of this level of the Shechinah resting on people were accomplished by the Nevi’im, and even for Klal Yisroel by Har Sinai when the Torah was given and like it says in Maseches Shabbos that their souls flew from their bodies, due to the extreme level of Bitul (Nullification) they experienced at the time. From the construction of the Mishkan until the destruction of the Beis HaMikdash there was always a clear place where the Shechinah rested, but now the only place for the Shechinah is in the Arba Amos Shel Halocho (four cubits of Halocho).
The key avodah of a Yid is to build a dirah b’tachtonim (dwelling place in the lower realms) for Hashem Yisborach. The way this is accomplished is through learning Torah in the way as proper for the person, as it says in Maseches Avodah Zarah that a person should learn Torah according to what they derive the most pleasure from, and performing every mitzvah possible throughout the day. The key goal is to attain spiritual joy, which occurs simultaneously as the Nefesh HaBahamis (Animal Soul) and Guf (Body) are considered shameful in the eyes of the eved Hashem. The way to understand this is not to enter into pathological hatred of corporeality, rather the approach should be recognizing that all desires of these lower aspects of the self are silly and worthless, since they are tied to this world rather than bound with the spiritual world. True joy can only come to a Yid through learning Torah as much as possible for him, ideally at least an hour in the morning and an hour at night. When a person fuses with the Torah and cleaves to Hashem through learning Torah, especially to the degree that one is constantly thinking of Torah and Hashem, then even physical needs and desires can be turned into a completely holy thing. When the joy of learning Torah and doing mitzvos overpowers the shame of physicality and all that comes along with it, then our mundane actions will also become holy. This is linked with what the S’fas Emes says about the M’raglim, that we should learn from them how to be shlichei mitzvah (agents to perform a mitzva) at all times. From the perspective that we are here only to fulfill Hashem’s will, and we completely dedicate ourselves to it every day through being m’kabel Ohl Malchus Shomayim (accepting the Yoke of the Heavenly Kingdom) and learning Torah, we can bring Hashem’s presence and light into everything in the corporeal world as we interact with it.