“Nevertheless…will I not…suffer my faithfulness to fail.” ~ Psalm 89 is all about the faithfulness of God (see vv.1,2,5,8,24,33,37).
You can depend on God. He’s always there when you need Him. You can be guaranteed that He’ll show up whenever and wherever there’s a need.
David failed God, but God would not fail David. All the times we are unfaithful to Him, “…he abideth faithful” to us. His faithfulness to us will never fail. In spite of our infidelity with the world, as with Hosea’s unfaithful wife, God says to us, “I will even betroth thee unto me in faithfulness.”
God pledged His faithfulness to us at the altar of our souls when we made our vows on the day of our salvation. He cannot, and will not, fail to keep His covenant. His faithfulness depends on His truthfulness; and, “God cannot lie."
Jeremiah knew this; and in spite of his viewing the utter destruction of Jerusalem, he reaffirmed, "Great is thy faithfulness," He did not judge God by what he saw or how he felt. Nor should we!