He compares us here to trees that flourish, or grow, in the courts of our God. As long as we keep praising Him, we will continue to grow. Just as the righteous flourished like trees in the courts of the Lord, we will also flourish as we enter into the courts of the Lord with praise. We need to always give Him praise and thanksgiving in order to grow spiritually. Jesus said that we are to bear good fruit.
Praise is the fruit of our lips.
We need to always proclaim the praises of God. We are not only to be inhabitors of praise, but praise should inhabit us.