The Jewish People are a unique nation. Usually someone who has a court case doesn’t know how the verdict will turn out, but when we approach the Day of Judgment of Rosh Hashanah, we are sure that we will win a good verdict. We wear nice clothing and eat, drink and rejoice on Rosh Hashanah because we are sure that G-d will make a miracle for us and give us a good verdict. The preparations begin already on Erev Rosh Hashanah, the day before the holiday starts, when it is customary to take haircuts and wash our clothes in honor of the holiday. Shabbos and Yom Tov need special preparation, and especially Rosh Hashanah, the head of the whole year, which influences the whole year.
(See talk of the Lubavitcher Rebbe King Moshiach Shlita, Erev Rosh Hashanah 5752 (1991))
