Well, Mark, far be it for me to answer any questions from a pastor, schooled in theology, but since you ask:
I think it always wise to read a verse within its entire context. David, a man after God’s heart, a firm believer in Israel’s God is in trouble. He needs help from God, he needs re-assurance, acknowledging that God is great and does wondrous things (verse 10). Isn’t that true of us when we are in difficulties? We can get down, from our own sinfulness or from situations not of our own making. That can make us feel low, even depressed, almost as if we are in hell. God promises to save us from whatever miseries that befall us. Look at the experience of Paul and Silas in a Philippian jail cell.
But, and I may be taking it out of context, look at verse 9 of this Psalm. That is wonderful news: “All nations whom Thou hast made shall come and worship before Thee, O Lord, and shall glorify Thy name”. Compare that verse with Phil. 2:10-11.