Rest becomes productive when it protects the person producing.

Rest counts as productive because it maintains the only thing doing the producing. Any measure of usefulness that excludes the condition of the person is measuring one quarter and calling it the whole, which is how capable people end up ruining the very capacity their results depended on.

Count your recovery as part of the work when you plan. Put it in the same list, with the same standing, and defend it as you would defend a deadline.