On Yom Kippur, we achieved sufficient atonement to warrant the entry of our representative in the holy of holies. Now that the Jewish people have reached that level, Succoth is the time at which all Jews have an opportunity to dwell in the house of the L-rd, namely, in a Succah. A Succah is a flimsy protection from the elements, reminding us that we live in the protection of G-d, not some wooden roof. On Succoth all Jews live in the house of the L-rd. We have taken the Temple and brought it home.

The Meaning of Lulav and Etrog

One midrash suggests that the lulav and etrog is a kind of victory symbol, marking the victory on Yom Kippur over our accusers in Heaven. One passage in the Talmud seems to indicate that the lulav is an arrow in the eye of the Satan, or a weapon to fend off bad thoughts, bad ideas, bad intentions. After Yom Kippur, we might be tempted to go astray, so the lulav helps us fend off bad deeds. Another meaning of the lulav is that it is an instrument of Hallel, thanksgiving. By waving the lulav, we give thanks to G-d for the harvest and for all of nature. It alludes to a world in which every creature serves a Divine purpose.