(The page numbers and layout are a bit different than the text I used, so you must adopt a little). The idea of חידוש was discussed at length in this class. The point the Rebbe is making is that the idea of חידוש is by a בעל תשובה. The Rebbe links this to שמחת תורה and the postponement of the joy of the Torah from Yom Kippur until Shmini Atzeres and Simchas Torah.
