John Gill Commentary Lamentations 3:21

"This I recall to my mind; therefore have I hope." — Lamentations 3:21 (ASV)

This I recall to my mind Not affliction and misery, but the Lord's remembrance of his people; what he had been used to do, and would do again; and particularly what follows, the abundant mercy of God, and his great faithfulness; these things the prophet fetched back to his mind; and revolved them in his heart; says he, and therefore have I hope ;

this revived his hope, which he was ready to say was perished from the Lord, and there was no foundation for it; but now he saw there was, and therefore took heart, and encouraged himself in the grace and mercy of God.