16 Yet he added, “But such shall have tribulation of the flesh, but I spare you:” in this manner exhorting unto virginity, and continual continence, so as some little to alarm also from marriage, with all modesty, not as from a matter evil and unlawful, but as from one burdensome and troublesome. For it is one thing to incur dishonor of the flesh, and another to have tribulation of the flesh: the one is matter of crime to do, the other of labor to suffer, which for the most part men refuse not even for the most honorable duties.
But for the having of marriage, now at this time, wherein there is no service done unto Christ about to come through descent of flesh by the begetting of the family itself, to take upon one to bear that tribulation of the flesh, which the Apostle foretells to such as shall be married, would be extremely foolish, did not incontinent persons fear, lest, through the temptation of Satan, they should fall into damnable sins. But whereas he says that he spares them, who he says will have tribulation of the flesh, there suggests itself to me in the mean while no sounder interpretation, than that he was unwilling to open, and unfold in words, this self-same tribulation of the flesh which he fore-announced to those who choose marriage, in suspicions of jealousy of married life, in the begetting and nurture of children, in fears and sorrows of childlessness.
For how very few, after they have bound themselves with the bonds of marriage, are not drawn and driven to and fro by these feelings? And this we ought not to exaggerate, lest we spare not the very persons, who the Apostle thought were to be spared.
Source: On Holy Virginity (New Advent)