Succos is a special holiday of simcha, as it is the completion of the cycle of the shalosh regalim and the Yamim Noraim. There are two mitzvos related to Succos that are halachos l’Moshe MiSinai, aspects of the Torah that cannot be explained or extrapolated from the text. Although most areas of Torah are for us to explore and derive, this area is to be taken just as it is, directly from Hashem. On the Yom Tov of Succos, we celebrate the ways that we were protected in the midbar, completely protected and supported by Hashem. No matter what human effort we put forth, we recognize that at the end of the day, it is all dependent on Hashem.