Since Rosh Hashanah is the day of Judgment, every person should be filled with fear and awe at his impending judgment. He should be careful to avoid anything that might bring him to levity or that might distract him from the gravity of this day.

So great is the fear of judgment among Israel on Rosh Hashanah, that they do not recite Hallel [Psalms 113-118, songs of praise recited on Festivals and the new months], even though Rosh Hashanah is a Festival. For the People of Israel recite Hallel before G‑d only when their hearts are filled with joy, and during the days of judgment there is more fear and trembling in Jewish hearts than rejoicing.

The ministering angels asked G‑d: "Master of the world: Why is it that Israel does not recite Songs of Praise on Rosh Hashanah and Yom Kippur?" G‑d replied: "When the King sits in judgment with the books of life and death open before Him - can Israel sing praise?" (Rosh Hashanah 32a).

Nevertheless, one should not be saddened by fear of judgment. Rather, one should shave and bathe in honor of the Festival and should wear his holiday clothing, thereby showing that we trust that G‑d shall judge us favorably. For the same reason one should not cry on Rosh Hashanah. During prayer, however, weeping is not forbidden and we therefore find persons of piety who weep like children during the prayers of Rosh Hashanah and Yom Kippur, to awaken the mercy of our Heavenly Father toward his children. Although we may be mature and learned, before G‑d we are each like a child who unashamedly weeps before his Father over the yearnings of his heart.

We see that this was the case when Ezra the Scribe read the Torah before the assembled nation who had gathered on the first day of the seventh month. The people wept when they heard the words of the Torah being read, and Ezra and Nechemyah told them (Nechemyah 8:10): Do not mourn and do not weep. Eat delicacies and drink sweet things and send gifts of food to those who lack, for the day is holy unto our Master. Do not grieve for G‑d's joy is your strength.

For is there another nation so great, that has statutes and laws so righteous as all this Torah... (Deuteronomy 4:7) - Which nation is like this one? Ordinarily, one who knows that he faces judgment dresses somberly, wraps himself in dark clothing, and lets his hair grow, for he is unsure regarding his future. But Israel is not like this: They dress in white and wrap themselves in white, and they eat and drink in joy, for they know that the Holy One, blessed is He, performs miracles on their behalf (Talmud Yerushalmi, Rosh Hashanah 1).