Everything they do is done for men to see. (Matthew 23:5)
A visiting minister on Sunday showed how big a problem self-righteousness is in the Christian family. He's in campus ministry and when I asked him how well the college students from Christian homes grasp the Gospel, he basically said that their parents have taught them self-righteousness and not the Christian Gospel.
He pointed out that as parents we are most happy when our children exhibit certain external behaviors and avoid others--this is our mark of success. We haven't taught them that Jesus was harshest with those who thought they had it together, who didn't acutely hate their sin and long for a Savior.
The minister added that parents just aren't as concerned with self-righteousness in their children as they are with "worldly" behavior, as if self-righteousness isn't twice as bad or dangerous. Despite all our effort in raising our children, if we're only teaching them how to behave, instead of modeling and exhorting them to continually repent and believe the Gospel, all we're doing is populating Hell.
You travel over land and sea to win a single convert, and when he becomes one, you make him twice as much a son of hell as you are. (Matthew 23:15)