We’re so blessed, you and I. For not only have we been granted the sheer and brimming gift that is Shabbat week after week, we’ve also been allotted other days rich in holiness (though mostly to a lesser degree than Shabbat’s). And all so that we can bask in holiness more and more.
Now, in keeping with the holy nature of such days, we’re asked to differentiate them from others. And the way to do that is to allot little time to worldliness on those special days. In fact, the holier the day, the less we’re expected to engage in the mundane.
Thus since, for example, it’s the holiest day of the year, we’re asked to refrain from doing many worldly things on Yom Kippur (even more than on Shabbat). Because the festivals of Rosh Hashanah, Passover, Succot, and Shavuot are of a lesser degree of holiness, they call for less restraint. And since the festival’s intermediate days (Chol HaMoed) are less holy yet, as are New Moons, Chanukah and Purim, they require even fewer restrictions.
At bottom, each day’s measure of holiness (and worldliness) is rooted in the amount and degree of light that shines in the course of it.