In the Responsorial Psalm we ask God to create clean hearts for us, and we ask him to give us steadfast spirits.
Clean hearts and steadfast spirits are usually conditions we think we acquire for ourselves by doing away with unclean thoughts and strengthening our resolves to keep going. Still, the Bible must know what it is talking about in leading us to ask God for those fine qualities.
The Bible there is reminding us that we never succeed on or own. Paul, writing to the people of Philippi said, “It is God working in you who causes you to will the good and to accomplish it.”
Paul also said, “God is not far from any of us, for in him we live and move and have our being.” We are like little fishes out in the ocean, with the ocean being God. There is no swerving to right or left independently of him.
But we do need to wiggle. We must do our part towards maintaining clean hearts. How worthwhile those efforts are! A clean heart, like a glistening glass, is a delight.