Parshas Vayakhel talks almost exculsively about building the Mishkan, however the first few pasukim are about the Mitzva of Shabbos. Chazal tell us that this teaches us that we are not allowed to build the mishkan on Shabbos. The Sridei Eish says there is another lesson that can be drawn from the parallel of the Mishkan and Shabbos.
Shabbos, says the Sridei Eish, is not the opposite of weekday, rather it is the culmination of the weekday. Before the world was created, Shabbos already existed. However in the creation Hashem made us a partner in Shabbos and this is the only kind of Shabbos He desired. Hashem made six work days that essentially are preparation for Shabbos. Friday night as we culminate our avodah of the week we say VaYichulu. and the gemara says that with this we become partners with Hashem in creation. If however our weekday is not geared towards building up Kedushas Shabbos, then Shabbos stands on its own not in accordance with Hashem's will for it in the creation.
Similarly, says the Sridei Eish, the pasuk tells us "V'Asu Li Mikdash V'Shacanti BiSocham", make Me a Mikdash and I will dwell among you. Hashem did not need a home but rather He needed us to "make" the Mishkan. The point was not to have a Mishkan but rather our effort in building it. It follows, says the Sridei Eish, that building a Miskan was not a one time Mitzva but a mitzva that continues even today despite that there is no Bais HaMikdash.
The fact that many Rishonim hold that the third Bais HaMikdash b"b will descend from Shamayim does not contradict this point, rather it proves it, says the Sridei Eish. In the Galus our mitzva of building a Bais HaMikdash does not mean building the structure. The true building of the Mikdash is through Torah and mitzvos. Chazal say that each generation that hasn't achieved its rebuilding, it is as if they destroyed it. And when the Bais HaMikdash finally descends complete from Heaven all the builders over the past 2000 years will share the credit for as much building as they did.
Chazal say that the Bais HaMikdash is a state of Shabbos. Whether in the galus or whether in the routine of the weekday we must realize that we are always working towards one goal, building the next Shabbos and at the same time the next Bais HaMikdash.