The psalmist does it again. He expresses honestly and beautifully the state of his own soul. He longs for salvation. He feels forgotten and alone.
Then he declares his trust in the Lord. While he presently knows loneliness and suffering, he also knows the steadfast love of the Lord. If the Lord is steadfast then certainly he is not actually alone. Even in the midst of suffering his heart can rejoice because the Lord’s salvation is sure.
I love the tension of the psalms. In verse 2 his heart is sorrowful. In verse 5 his heart rejoices so that the psalm ends with singing.
This psalm is an invitation to the suffering to join in this song. Sure the Lord has and will deal bountifully with me.