Faith is the antidote for fear. David expresses total confidence in God. After all, when the Omnipotent is your strength and salvation, who should make you afraid?
The greatest desire of David's heart is seen here as well. More than anything he longs for the presence of God. He seeks the face of God with singleness of purpose.
One thing. It becomes the driving purpose of His life.
What is your "one thing?" The proof is not in what we say, but what we seek.