Friends, today Jesus tells us of the Pharisee and the tax collector—so, stereotypically righteous and unrighteous people—who both enter the Temple to pray. But what a world of difference in their manner of praying!
The entire point of religion is to make us humble before God and to open us to the path of love. Everything else is more or less a footnote. Liturgy, prayer, the precepts of the Church, the Commandments, sacraments, sacramentals—all of it—are finally meant to conform us to the way of love. When they instead turn us away from that path, they have been undermined.
Both St. Paul and the Gospel writers—as well as Jesus himself, of course—are intensely aware of this danger. This is precisely why Paul speaks of the dangers of the Law. He knew that people often use the Law as a weapon of aggression: since I know what is right and wrong in some detail, then I am uniquely positioned to point out your flaws. And when I point out your flaws, I elevate myself. In short, the Law, which is a gift from God, has been co-opted for the purposes of the ego.