Rules a person has to force themselves to keep are rules attached to a name they have not yet taken.
Holiness gets conferred before it gets practiced, and that order is what makes the conduct possible. The definition is drawn from Yahweh's own, so the standard is not a target the people set and can quietly revise downward. Once that label is carried, the pull toward the creeping thing does not have to be beaten; it stops matching who they now are, and behavior that contradicts an identity does not survive long enough to harden into habit.
Reverse the order and the whole thing becomes willpower, where each act of restraint is a fresh negotiation with a self that still wants the thing, and tomorrow the negotiation reopens. A person paying that way spends on every meal the energy meant for everything else in the life.