The teaching of my father-in-law the [Previous] Rebbe is well-known, that when Mashiach comes people will regret that the best days, the last days of the period of exile, have passed. For those were times when one was able to engage in Torah and mitzvos despite all obstacles and all obscurity; times when one's divine service was more gratifying and more lovable, both for the mortal who did it and for his Maker Who commanded that it be done; times unlike the future time, when "I shall remove the spirit of impurity from the earth," and when there are no antagonists to contend with.