What does Psalm 21:7 mean?

This repeats David's unshakeable confidence in God; this is a trust founded in God's own character and faithfulness. None of David's enemies would shake him from the throne. God favored King David too much for an enemy to topple him. He would continue to complete the mission God had designed for him.

Believers may experience suffering, difficulties, deprivation, and persecution, but nothing can separate them from God's love revealed in the Lord Jesus. Romans 8:37 asserts that "in all these things we are more than conquerors through him who loved us." The following two verses tell us, "neither death nor life,; nor angels nor rulers, nor things present nor things to come, nor powers, nor height nor depth, nor anything else in all creation, will be able to separate us from the love of God in Christ Jesus our Lord" (Romans 8:38–39).

Our circumstances often change, but God's love for us is changeless.