The nature and character of God is of course worthy of all praise and adoration. But we are finite, and sinful on top of that, and so we cannot even begin to praise Him as He deserves to be praised. Nevertheless, the effort must be made. As forgiven sinners, how on earth are we going to declare His worth? What are we going to do? Shout? Stand on a chair?
One of the ways that Scripture assigns to us is the method of declaring His works—the mighty works that He accomplished down here where we live. This is something we can do, and David shows us the way.