Let that which was then said by our Lord be the general maxim for every life; especially let it be the maxim for those who are coming nearer God through the gateway of virginity, that they should never in watching for a perfection in one direction present an unguarded side in another and contrary one; but should in all directions realize the good, so that they may guarantee in all things their holy life against failure. A soldier does not arm himself only on some points, leaving the rest of his body to take its chance unprotected.
If he were to receive his death-wound upon that, what would have been the advantage of this partial armour? Again, who would call that feature faultless, which from some accident had lost one of those requisites which go to make up the sum of beauty? The disfigurement of the mutilated part mars the grace of the part untouched. The Gospel implies that he who undertakes the building of a tower, but spends all his labour upon the foundations without ever reaching the completion, is worthy of ridicule; and what else do we learn from the Parable of the Tower, but to strive to come to the finish of every lofty purpose, accomplishing the work of God in all the multiform structures of His commandments?
One stone, indeed, is no more the whole edifice of the Tower, than one commandment kept will raise the soul's perfection to the required height. The foundation must by all means first be laid but over it, as the Apostle says, the edifice of gold and precious gems must be built; for so is the doing of the commandment put by the Prophet who cries, “I have loved Your commandment above gold and many a precious stone.” Let the virtuous life have for its substructure the love of virginity; but upon this let every result of virtue be reared.
If virginity is believed to be a vastly precious thing and to have a divine look (as indeed is the case, as well as men believe of it), yet, if the whole life does not harmonize with this perfect note, and it be marred by the succeeding discord of the soul, this thing becomes but “the jewel of gold in the swine's snout” or “the pearl that is trodden under the swine's feet.” But we have said enough upon this.
Source: On Virginity (New Advent)