In faith, you have become part of Christ's body, and it is Christ through the Church, who must give you permission to join His body to another body. The place where the Church confers that privilege on you is the wedding; weddings are specific acts that grant us permission to have sex with one person. The New Testament makes clear that sex beyond the boundaries of marriage — the boundaries of communally granted sanction of sex — is simply off limits.
To have sex outside those bounds is to commit an offense against the body.
In fact, the opposite is true: The dramas of married sex are smaller and more intimate, and in fact it is the stability of marriage that allows sex to be what it is.
Even when you've been dating someone for a year, the lack of permanence that characterizes your relationship seems to add a certain frisson to everything you do with that person, from going on a Saturday hike to smooching on the sofa. It becomes a ritual in itself; it becomes a routine.Married sex does not derive its thrill from the possibility of the unknown. It is based on mutual desire, and it dispenses with the ordinary rhythms of marital sex, trading them for a seemingly thrilling, but ultimately false, story.This may be the way that the sin of premarital sex sticks with us most lastingly; it may be the twisted lesson it teaches us most convincingly: That sex derives its thrill from instability and drama.We talk about the possibility of STDs, or unwanted pregnancy — we talk about cheapening something that God intended us to participate in with only one other person.All those points are true, of course, but the most essential truth of chastity is that in turning away from certain expressions of sexuality and romanticism, we can allow ourselves to focus on God in a particular way that would otherwise not be possible.