Not only on Rosh HaShana, when a person recites Psalms 47 seven times, nor on Yom Kippur, when a person cries out Shema Yisrael during the Ne’ila service, but rather, a person must serve God as His servant also on a regular weekday when he dons the tallit and tefillin.
The existence of all the worlds depends on this.
Rabbi Adin Steinsaltz