The psalms are optimistic because they offer hope for the future. In psalm 17:51, God will show “mercy to David and his anointed: and to his seed forever”. This means that God will show mercy to David’s inheritance. This offers David hope for the future. In psalm 24:13, for the man who believes in God, “his soul shall dwell in good things, and his seed shall inherit the earth”. This offers hope for God’s believers. In psalm 15:5, “the Lord is the portion of my inheritance and of my cup: it is thou that wilt restore my inheritance to me”. God will preserve David’s inheritance. These psalms show the optimism of the psalmist, and his hope for the future.