Your cry of exhaustion is one that many of the Lord's people have known, for human strength in any form will spend itself in due time. All strength apart from God is derived strength and is consequently measurable, and must come to an end. When body and mind are spent, we are made to feel that if a duty is to be performed at all, it cannot be done in the strength of nature.
But there is a promise that meets you in this very weakness. Do you not know that He gives power to the faint and to them that have no might He increases strength. They that wait upon the Lord shall renew their strength. To wait upon Him is to look to Him, to trust Him, to stay your mind upon Him, and then strength is given, for the Lord Himself declares, I will strengthen them. It will be fitly infused and wisely balanced, and though it may be gradually received, it shall surely come. When there remains no strength in you, then fling yourself upon the Divine strength and lay hold upon it.
And with that strength He gives peace. You will keep him in perfect peace, whose mind is stayed on You, because he trusts in You. This is not a peace for some future day alone, but a present possession to be enjoyed in the ordinary circumstances of life. In this dark world of sin the blood of Jesus whispers peace within. When duties press and sorrows surge round, to do the will of Jesus, this is rest. Bear your weariness with Him and see what perfect peace you will enjoy, for the Lord has endless, boundless peace within Himself and He will bless His people with peace.
He also has a gift for the weary body. So He gives His beloved sleep. There is a sleep of contentment and a sleep of security which the Lord bestows upon His own, a means of refreshment by the recruiting of exhausted strength to fit us for fresh exercise when we awake. As one who has a quiet conscience at peace with God, you may lie down and say, I will both lay me down in peace and sleep, for You, Lord, only make me dwell in safety.
I pray for you now that the Lord will surround you with His presence this night, that He will keep your mind stayed upon Christ and whisper perfect peace within, that He will grant you deep and restorative sleep as He gives to His beloved, and that you will awake renewed in strength, your peace as a river, fitted for the duties of tomorrow. May He who neither slumbers nor sleeps watch over you and cause you to rise as one who has been bathed in the Spirit of God, strong in the Lord. In the name of Jesus Christ our strength and our peace, Amen.