In your good pleasure make Zion prosper;
build up the walls of Jerusalem.
Zion is God's kingdom. And David is praying that God would do good to His kingdom. These words are similar to the words of Christ when the example prayer was prayed for the disciples. Jesus prayed, "...Thy Kingdom come, Thy will be done, on earth as it is in heaven..."
When we recover from sin, our thoughts should begin to go back to where they belong: On God and his expanding kingdom.
No longer are we going to be dwelling on selfish thoughts: on how we are doing, on how our lives are playing out, on what we are getting out of different situations. We will begin to think on others. We will begin to think about how we can meet the needs of others and serve them, all for the advancing of the kingdom.