In accordance with the well-known instruction of the Baal Shem Tov, a Jew should learn from everything he sees and hears. December 5, 1987 was the anniversary of the Rebbe's wedding (14 Kislev), the Rebbe then announced that we need to complete all the prep work in exile in a manner of "the blow of the hammer". Hence, the Rebbe concluded: if anyone hears the sound of a hammer, then they need to know that the only reason for this is to remind them of the need to complete their personal "work." But what exactly is this work or where is that last nail waiting to be hammered in?
According to the Rebbe, we do not know the exact answer, that's why we need to perform another commandment and then another, and another ... Then it is possible that among them would be that which was required of us to do. Four years later, in 1991, the Rebbe told us that all the work in exile had been completed and we need to greet Moshiach, in actuality. Therefore, by fulfilling mitzvos, we must bear in mind that the world is already fixed and this is only necessary for the Redemption to begin unfolding.