25 The past day returns not hereafter, and after yesterday proceeds today, and after today will proceed tomorrow; and, lo, all times and the things of time pass away, that there may come the promise that shall abide; and “whoso shall have persevered even unto the end, this one shall be saved.” If the world is now perishing, the married woman, for whom bears she? Or in heart about to bear, and in flesh not about to bear, why does she marry? But if the world is still about to last, why is not He more loved, by Whom the world was made?
If already enticements of this life are failing, there is not any thing for a Christian soul with desire to seek after; but if they shall yet remain, there is what with holiness he may despise. For the one of these two there is no hope of lust, in the other greater glory of charity. How many or how long are the very years, in which the flower of carnal age seems to flourish? Some females having thoughts of marriage, and with ardor wishing it, while they are being despised or put off, on a sudden have grown old, so as that now they would feel shame, rather than desire, to marry.
But many having married, their husbands having set out into distant countries very soon after their union, have grown aged expecting their return, and, as though soon left widows, at times have not even attained so as at least as old women to receive their old men on their return. If therefore, when betrothed bridegrooms despised or delayed, or when husbands were abroad, carnal desire could be restrained from commission of fornication or adultery, why cannot it be restrained from commission of sacrilege?
If it has been repressed, when being deferred it was glowing, why is it not put down, when having been cut off it had grown cold? For they in greater measure endure glowing of desire, who despair not of the pleasure of the same desire. But whoso of unmarried persons vow chastity to God, withdraw that very hope, which is the fuel of love. Hence with more ease is desire bridled, which is kindled by no expectation; and yet, unless against this prayer be made, in order to overcome it, itself as unlawful is the more ardently wished for.
Source: On the Good of Widowhood (New Advent)