We are on earth only to render ourselves worthy of heaven. But heaven is not given; it has to be purchased. Little children who die after Baptism receive it without personal merit, it is true. Our Lord pays for them, but adults receive it only on a title of justice, Coronam justitice. True it is that God gives us the means of meriting it, but we must correspond with His grace and faithfully employ those means. He gives and He recompenses in us His own gifts, if we have rendered them fruitful. Thus does He reconcile the goodness of His mercy and the requirements of His justice.
--St. Peter Julian Eymard
