I think good works are simply being a good example. That means being a faithfull person in whatever your calling is. If it is a parent, it means being a good example for your children. Sacrificing your own needs for those of your children. Teaching to have faith in God through your own example. Like going to church.
Mother Theresa is a perfect example of someone who lived her Catholic faith. It is looking at someone who talks of God, and others can see her love, in action, as well as words. Like they say, "talk is cheap".
So if you fail at being a good example is that a sin?