He had said "Let’s go through this together. Let me help." And He had proven Himself again and again. But there’s something deep inside us that diminishes past facts and magnifies present uncertainties. Somehow God’s faithfulness in the past doesn’t carry weight for long and pretty soon we start feeling as unloved and alone as ever. It’s just the way we are. That’s why we need constant renewal. There is always some plausible alternative to trusting in God, something to take our eyes of God.
From the book "Isaiah: God Saves Sinners (Preaching the Word)"