Yom Kippur (the Day of Atonement) is a long day.
Like, really, really long.
Services start at 10am and they end around 6pm (this is for our shul (synagogue), many others will have different schedules), with small breaks in between. Those who are able should also fast from sundown the night before until the fast is “broken” after Havdalah (the service that ends “holy time” celebrated at the end of Shabbat and holidays) at the “end” of Yom Kippur. This means that a person is sitting through hours of services while thirsty and hungry. (Full disclosure: I was unable to fast this year because my blood sugar is very wonky right now, and I’ve had far too many issues/episodes lately. So, I ate lightly and small to regulate my blood sugar.)
Yom Kippur is also beautiful. It is edifying to come together as a community, pray with other Jews the same prayers being said throughout the Jewish world. The sanctuary is packed to the gills, familiar and new faces both plentiful. We start at the beginning of the Machzor (our prayer book used for High Holy Days) and at the end of the day, we will have reached the end, some 600+ pages later.