We can compare this to that which is written at the beginning of sefer BaMidbar, when Hashem instructs Moshe and Aharon to count the Jewish people. The Ramban (BaMidbar 1:45) writes that this was to give the Jewish people an opportunity to stand before Moshe and Aharon. The Ramban writes, "When one comes before the greatest navi [Moshe] and his brother [Aharon] and tells them his name, this is a merit for him, and it grants him life because he is being counted together with the Jewish nation. Moshe and Aharon will look at them with a good eye and pray for them."
Certainly, to be in Hashem's presence is a blessing, resulting in spiritual and material success. This occurs on Rosh Hashanah because Chazal tell us that on Rosh Hashanah each person passes before Hashem, individually.
On Rosh Hashanah and Yom Kippur, we repeat the word ובכן in Shemoneh Esrei numerous times. Abudraham explains that the word comes from the pasuk (Esther 4:16) ובכן כדת לא אשר המלך אל אבוא, "And then I will go to the king..." because, on Rosh Hashanah, we come before the King, Hashem. Rebbe Yehoshua of Belz zt'l explains that the main lesson of the pasuk is לא אשר המלך אל אבוא ובכן כדת, "and then I will go to the king, which isn't proper." The pasuk refers to sinners who may be unworthy of coming to the King. On Rosh Hashanah and Yom Kippur, they can come to the King, and Hashem accepts their tefillos.
As we say in the tefillos of Rosh Hashanah, וגדול קטן ומשוה, "Hashem acts equally towards the small and the great people."
Reb Saadya Gaon says that it used to be the custom to blow horns at the inauguration of a king. When we blow the shofar on Rosh Hashanah, we announce Hashem as King. When we think about our privilege on Rosh Hashanah, we understand the immense joy. Who are we to announce and crown Hashem? Who are we to stand before Hashem's throne, speak with Him, and connect with Him? This is our immense joy on Rosh Hashanah.
The Imrei Chaim of Vizhnitz zt'l says that the roshei teivos of שופרות זכרונות ,מלכיות spell ז"שמ. Add one more (the kollel), and it is ח"שמ. Our great joy on Rosh Hashanah is that we proclaim and appoint Hashem king. The great joy of Rosh Hashanah is that we do so as we stand before His glorified presence.
Chazal tell us that on Rosh Hashanah, every Yid passes before Hashem מרון כבני, like sheep that pass through a gate, one by one. The Sfas Emes (5639) writes, "Although they know that Hashem is judging them, nevertheless, every Yid understands that it is a great merit to be remembered by Hashem. They consider it worthwhile to be judged by Him just so that Hashem will think about them. And in the merit that they feel this privilege, Hashem thinks of them. Hashem remembers all the good they do, and He goes off His throne of justice and sits on His throne of compassion. They deserve this because they understand that the greatest good they can receive from Hashem is that Hashem thinks about them."
