8 So much for dress and adornment. But a widow “that lives in pleasure”— the words are not mine but those of the apostle— “is dead while she lives.” What does that mean— “is dead while she lives”? To those who know no better she seems to be alive and not, as she is, dead in sin; yes, and in another sense dead to Christ, from whom no secrets are hid. “The soul that sins it shall die.” Some men's sins are open...going before to judgment: and some they follow after. Likewise also good works are manifest, and they that are otherwise cannot be hid. The words mean this:— Certain persons sin so deliberately and flagrantly that you no sooner see them than you know them at once to be sinners.
But the defects of others are so cunningly concealed that we only learn them from subsequent information. Similarly the good deeds of some people are public property, while those of others we come to know only through long intimacy with them. Why then must we needs boast of our chastity, a thing which cannot prove itself to be genuine without its companions and attendants, continence and plain living? The apostle macerates his body and brings it into subjection to the soul lest what he has preached to others he should himself fail to keep; and can a mere girl whose passions are kindled by abundance of food, can a mere girl afford to be confident of her own chastity?
Source: Letters (New Advent)