I once heard someone say that the ultimate measure of a song comes down to one thing; does it move someone?
I continually find this to be true. If a song does not stir me then how can I expect it to stir anyone else. With that said, how can I expect it to stir the Lord?
There is an old saying, that while crass, rings true even now. "Poop or get off the pot". The idea is that you can write lyrics all day long. You can write cord progressions that flow beautifully, but neither of these mean that a song is found within them.
Don't try to sing when you don't have anything to say. Make absolutely sure that each song contains a part of yourself. If your heart is the thing that God wants in worship, then make sure that your heart is given each time you offer a song. In that sacrifice of yourself you offering will be a sweet smelling savor before the Lord.