The Day of Judgment is not only after death or at the end of the world; rather, all people stand in judgment before God each year on Rosh HaShana, and there is a great kindness in this.

Why does one need to stand in judgment before the Creator every year?

The reasons for the mitzva of this festival include: That it was one of the kindnesses of God to His creatures to remember them and examine their deeds on one day each year, so that their sins will not proliferate, and the possibility of atonement will remain. He is “abounding in kindness” (Exodus 34:6), inclined toward kindness, and since [the sins] are few, He tolerates them [and does not punish]. If perhaps there are among them sins that [defile the sinner] and require cleansing [i.e., punishment], He punishes them little by little, and this is like what the Sages said: “His beloved, He punishes him little by little” (Avoda Zara 4a). If He did not reckon with them for a long period, [their sins] would proliferate so much that the world would almost be deserving of destruction, God forbid.

That being so, is Rosh HaShana a day of celebration or a day of fear and trembling?

Consequently, this important day [ensures the continuing] existence of the world, and therefore it is fitting to make it a festival, and it is fitting for it to be counted among the special periods of the year. Nevertheless, as it is the day of the judgment of all living beings, it is appropriate to stand in fear and awe on it, to a greater extent than on any of the other festivals of the year. This is the idea of “a remembrance by means of an alarm blast [teru’a]” (Leviticus 23:24), mentioned with regard to [Rosh HaShana], as the teru’a is a fragmented sound, indicating that each individual should shatter the force of his evil inclination, and should regret his evil deeds. (Sefer HaĤinnukh 311)

Further reading: For more on Rosh HaShana, see A Concise Guide to the Torah, p. 317; A Concise Guide to the Sages, p. 282; A Concise Guide to Halakha, p. 129.

God watches over all the deeds of mankind, and when the Day of Judgment comes, the accusers present our evil deeds, but God directs the ruling in accordance with His will.

On Rosh HaShana, the angels stand before the Creator, and among them is the accusing angel:

Rabbi Elazar began [his homily]: “It was one day, and the children of the great came to stand before the Lord, and the accuser too came among them” (Job 1:6). “It was one day”: This is Rosh HaShana, when the Holy One, blessed be He, stands in judgment over the world. Similarly: “There was one day that he came there” (II Kings 4:11). That day was the festival of Rosh HaShana.

God rules in favor of Israel:

“The children of the great came”; these are the great angels appointed and sent into the world to observe the actions of human beings. “To stand before the Lord”; as it is stated: “All the host of the heavens attending Him on His right and on His left” (I Kings 22:19). “The accuser too came among them…” “Too”: To include him over them, as they all come to serve as accusers of Israel, and this one is added to them because he is the greatest denouncer of them all, the greatest accuser. When the Holy One, blessed be He, sees that they are all coming to accuse, immediately, “the Lord said to the accuser: From where have you come?” (Job 1:6). Did not the Holy One, blessed be He, know where he had come from? Rather, it is to direct the [accuser’s] action by His will. (Zohar 2:32b)

Further reading: The combination of joy and of trembling due to the fear of judgment is also expressed in the festival meals; see A Concise Guide to Halakha, p. 141.