1) On the night following Yom Kippur, we eat and drink and rejoice, as it is a partial festival. In the Midrash it is written that on this evening a bas kol (divine voice which sounds like an echo) proclaims “Go and eat your bread with rejoicing, and drink your wine with a good heart, for Hashem has already accepted your deeds!”. (Shulchan Aruch and Mishne Berurah 624)
1) It is a good thing to build one’s Sukkah immediately on the night after Yom Kippur as “A good deed which comes into your hand should not be left to go sour!”. One who is careful with his actions should commence building even if he cannot finish it that evening, and finish it the next day. Even one who is not careful should at least start the next day and try and finish it all on that day if possible. (ibid 625)