The clearest expression of our self-righteousness is our belief that people go to hell for their sins.
Christian/Catholic orthodoxy teaches us that we can determine who goes to heaven and who goes to hell by judging what people have done or not done. In this view, a person’s destiny depends not on what God accomplished through Jesus, but on how that person responds to what God has done. This is the definition of self-righteousness.
(Thankfully, it is our self-righteousness and lie that demonstrate His righteousness and truth. Let God be true, and every man a liar.)