Most of us have a strong sexual drive that we would like to satisfy in marriage. But we also know that marriage is vastly more than an outlet for sexual satisfaction. In fact we know that if our passions are not submitted to something much higher even sexuality itself is ruined. So Paul goes on to tell us what that higher reality is. In other words knowing God should transform the way we fall in love and get engaged and get married and the way we relate sexually in marriage.
Sexual passion is real.
Marriage is God's appointed place of its consummation. But the reality of God in our life should utterly transforms the way we satisfy our passions. God is a God of the bedroom or no God at all. Then in the latter half of verse 6 Paul shoots his rifle over their heads. As if to say, brothers I'm not kidding, this is serious.