Good Comes After Hardship
Rav Moshe teaches that the good cannot be reached until sorrow and sighing have first passed over a person. A generation must be refined through hardship before it is fit to receive good, just as the generation of the desert was refined over forty years before it entered the Land. The Egyptian exile and the years in the desert were the preparation for the good that followed.
Source: Melekhet Machshevet, Chumash commentary (as cited in Hidabroot)