You and I are not faithful and just, but God is. He will answer our prayers because of His Goodness, not ours (Ps 143:1).
You and I don’t naturally choose the right ways of life, but God always does. That’s why we must be taught to do His will (vs 10).
If He is truly “my God,” then I am “His servant” (vs 12). If I am His servant, I should do His will. “Teach me to do Your will, O’ God.”