Remember that God does not grow weary.
“Do you not know? Have you not heard? The Everlasting God, the Lord, the Creator of the ends of the earth Does not become weary or tired. His understanding is inscrutable.” Isaiah 40:28 NASB
Look to Him to sustain and refresh you
“Come to Me, all who are weary and heavy-laden, and I will give you rest.” Matthew 11:28 NASB
Ask Him for strength
“The Lord is my strength and my shield; in him my heart trusts, and I am helped; my heart exults, and with my song I give thanks to him.” Psalm 28:7 ESV