"The everlasting God . . . fainteth not, neither is weary." Isaiah 40:28
Exhaustion means that the vital forces are worn right out. Spiritual exhaustion never comes through sin but only through service, and whether or not you are exhausted will depend upon where you get your supplies. Jesus said to Peter - "Feed My sheep," but He gave him nothing to feed them with. The process of being made broken bread and poured out wine means that you have to be the nourishment for other souls until they learn to feed on God. They must drain you to the dregs. Be careful that you get your supply, or before long you will be utterly exhausted. Before other souls learn to draw on the life of the Lord Jesus direct, they have to draw on it through you; you have to be literally "sucked," until they learn to take their nourishment from God. We owe it to God to be our best for His lambs and His sheep as well as for Himself.
Has the way in which you have been serving God betrayed you into exhaustion? If so, then rally your affections. Where did you start the service from? From your own sympathy or from the basis of the Redemption of Jesus Christ? Continually go back to the foundation of your affections and recollect where the source of power is. You have no right to say - "O Lord, I am so exhausted." He saved and sanctified you in order to exhaust you. Be exhausted for God, but remember that your supply comes from Him. "All my fresh springs shall be in Thee."