sufficient unto the day

     . . . for what so strong,

     But wanting rest will also want of might?
     The Sunne that measures heauen all day long,
At night doth baite his steedes the Ocean waues among.

Then with the Sunne take Sir, your timely rest,
     And with the new day new worke at once begin:
     Vntroubled night they say giues counsell best.

     The Lady to the Knight of the Red Crosse, Edmund Spenser, The faerie queen I.i.32 l.6-33 l.3.
     Not that that sleep turned out to be without its dangers, the "faire discourse" and "Aue-Mary" notwithstanding!  (Or maybe the pair should have known better than to have "told of Saintes and Popes" and "strowd an Aue-Mary".)