By Rabbi David Cohen:
The Chag of Sukkot serves as a reminder that we only live in this world temporarily. Just as the flimsy structures we sit in for seven days are temporary dwellings and we would never wish to end up there permanently, so too, our entire sojourn in this world is but a temporary existence.
The Alshich Hakadosh, R’ Moshe Alshich explains that this is the reason why the holiday is called “Chag HaSukkot” and not any of the other mitzvot that we do at this time, like Arba Minim or Nisuach HaMayim. It is because all the elevated levels of saintliness that a person wishes to reach in this world are dependent on one thing, and one thing only: How much he internalizes the fact that he is a living in this world as a temporary resident. All his possessions are meaningless; in fact, they aren’t even his.
A Jew must come to the realization that all his money and assets in this world are temporary and minor, and Olam Haba, is the enduring and permanent dwelling.