On Rosh Hashanah it’s decided how much money one will earn over the course of the entire year. The money spent on Talmud Torah (schar limud), Shabbos,
Rosh Chodesh and Yom Tov is not included in this calculation.

Rosh Hashanah is the first day of the month of Tishrei. תשרי is an acronym for Talmud Torah, Shabbos, Rosh Chodesh and Yom Tov.

Sukkos is known as Z’man Simchaseinu (the Festival of Joy) because it shows Hashem’s love for the Jewish people. Sitting in the sukkah is akin to getting a hug from Hashem because one is surrounded from all sides by the sukkah.

Sukkos has seven days. When you multiply the gematria of Ahava (13) by 7, it equals 91, which is the gematria of Sukkah.
אהבה x 7 = 91 סוכה

The Gemara Rosh Hashanah relates that on Rosh Hashanah Hashem has three books – one for tzaddikim, one for reshaim, and one for beinonim (those who have both mitzvos and aveiros). Tzaddikim and reshaim are signed and sealed in their respective books immediately, but the book of the beinonim is not closed until Yom Kippur. The question that needs to be asked is, “Why have a separate book for beinonim at the end of Yom Kippur? Why not inscribe each one either in the book of tzaddikim or the book of reshaim?” The answer is that those who do teshuvah are on an even higher level than a tzaddik, so they cannot be listed in the book of tzaddikim and need their own separate book.