The author is searching for hope. Hope for a return to a time when he was happy. A time when he did what he desired. He desired to praise the Lord with the harp, his stringed musical instrument. He desired to be able to go to the altar of God as he had once before. The Sons of Korah turn to God for help. They put their trust in the Lord Jesus.
In this world, trouble comes at a sudden notice, an oppression from without persists to annoy. The enemy comes and removes us from the place where life was good. The enemy attacks are when I need to place my hope in the Lord my God.
Why am I downcast? Why am I disturbed within me? Put my hope in God. I hope in God. He lifts the oppressed. He comforts the disturbed. I will again be in a happy place serving the Lord. Hope in my Savior and my God.