Coal, which is one of our most vital sources of energy, can only be extracted by digging deep beneath the surface of the earth.
The miners who descend into a coal mine must follow an expert's directives on where to dig and how to find the coal. However, while the miner can rely on the guide's directives for where to dig, no one can breathe for him. Each miner must be connected to a supply of air way up above the place where he is working. If not, he will not be able to remain alive.
The study of Chassidus, the inner aspect of Torah, is analogous to this "descent". The knowledge gained from learning Chassidus imparts light and warmth, but one must delve deeply into it in order to fully appreciate its brilliance.
And like the miner, the student of Chassidic thought must remain connected to his spiritual source, if his divine service is to have life.
Then, as with coal, one must light a fire - approach the material to be studied with warmth and enthusiasm - if it is to provide light and warmth on a daily basis.
Sefer HaSichos 5705, p. 50