Derekh Hashem, Part Four, On the Daily Order of Prayer

Days upon which there is no tefillin: And behold we were commanded to be crowned with this crown every day except for holy days - which are themselves a sign for Israel. Hence Israel is crowned through them (the holidays) without any other effort - which is not the case on other days. For it is impossible to acquire the crowns [then] without this effort (of tefillin). But even after this personal effort, the crown that is achieved by them is not on the level of the crown achieved automatically on holy days, but rather much less than it. Yet all things are determined according to what is most appropriate, with all of their limits, by the Supreme Wisdom, .