14 “Wait on the Lord, quit yourself like a man: and let your heart be strong, yea wait on the Lord”. But when shall this be? It is arduous for a mortal, it is slow to a lover: but listen to the voice, that deceives not, of him that says, “Wait on the Lord.” Endure the burning of the reins manfully, and the burning of the heart stoutly. Think not that what you do not as yet receive is denied you. That you faint not in despair, see how it is said, “Wait on the Lord.”
Source: The Enarrations, or Expositions, on the Psalms (New Advent)