"God, who formerly had abandoned Israel, is asked to return to them, and what men cannot do, God most certainly can. Through God we will do valiantly---and that is the only way we will do valiantly." See verses 10-12.
David inherited a royal mess. Understanding the politics and the culture, David conducts an honest inventory of Israel asking God to come back and give true restoration. David is able to end the Psalm in triumph because he knows God's promises. God has promised salvation for this world and that His Spirit will fill it. He knows God's promises and is triumphant in them.
Israel was at a point where no one would have known who they were but a handful of archeologists. First we must have honesty about the sin, secondly about your Saviour. Look at God's Law and our behaviour and see why God is displeased. Salvation must be declared. The Saviour's name must be honoured. You cannot run around shouting about how the Philistines oppress and then when saved whisper under your breath that God saved you. You thank God out loud! You honour Him!
"If God has declared that something will come to pass, then he is no fool who counts on it coming to pass, and who labours toward that end." God has picked up the promise of Canaan and expanded it. It's not a question of whether it happens, but a question of when. The world is going to be full of the sons of Abraham.
Vain is the help of man, but at the same time "through God we shall do valiantly."
"A strong confidence in the ultimate and complete authority of God does not lead to a passive quietism." There is no salvation, no help in Christless anything, i.e. the tea party, conservatism, etc. These may be good common sense things but don't think that common sense can save you. Nothing can be sustained apart from Christ. Is He the Lord of our abortion policies, finances, immigration laws, social security policies? Then act like it. This is not a 50/50 relationship, nor is it 90/10. God does 100% and we do 100%. You are not a hand puppet. If we are wanting God to do it all we are misunderstanding the soveriegnty of God. Apart from faith and His encouragement we would not be doing any of this. God is at work in us. Christ is being formed in us. So take notice of what you are shaping into.