6 I have spoken thus, my daughter in Christ, not because I doubt that you will be faithful to your vows, (you would never have asked for a letter of advice had you been uncertain as to the blessedness of monogamy): but that you may realize the wickedness of servants who merely wish to sell you for their own advantage, the snares which relations may set for you and the well meant but mistaken suggestions of a father. While I allow that this latter feels love toward you, I cannot admit that it is love according to knowledge.
I must say with the apostle: “I bear them record that they have a zeal of God, but not according to knowledge.” Imitate rather— I cannot say it too often— your holy mother whose zeal for Christ comes into my mind as often as I remember her, and not her zeal only but the paleness induced in her by fasting, the alms given by her to the poor, the courtesy shown by her to the servants of God, the lowliness of her garb and heart, and the constant moderation of her language. Of your father too I speak with respect, not because he is a patrician and of consular rank but because he is a Christian.
Let him be true to his profession as such. Let him rejoice that he has begotten a daughter for Christ and not for the world. Nay rather let him grieve that you have in vain lost your virginity as the fruits of matrimony have not been yours. Where is the husband whom he gave to you? Even had he been lovable and good, death would still have snatched all away, and his decease would have terminated the fleshly bond between you. Seize the opportunity, I beg of you, and make a virtue of necessity.
In the lives of Christians we look not to the beginnings but to the endings. Paul began badly but ended well. The start of Judas wins praise; his end is condemned because of his treachery. Read Ezekiel, “The righteousness of the righteous shall not deliver him in the day of his transgression; as for the wickedness of the wicked he shall not fall thereby in the day that he turns from his wickedness.” The Christian life is the true Jacob's ladder on which the angels ascend and descend, while the Lord stands above it holding out His hand to those who slip and sustaining by the vision of Himself the weary steps of those who ascend.
But while He does not wish the death of a sinner, but only that he should be converted and live, He hates the lukewarm and they quickly cause him loathing. To whom much is forgiven, the same loves much.
Source: Letters (New Advent)