I see sex as the means by which God allows a man and a woman to participate in one of the greatest miracles He has ever performed: that of creating new life. Life, I believe, is so sacred that the process by which it is initiated should be sacred as well. When a child is conceived, a simple biological process takes place in which a single cell divides, once, twice, three times and, ultimately millions and millions of times. Organs develop, arms and legs, tiny eyes, ears, noses and mouths are formed, and we say that life is created. But that child isnt really a living soul until the real Creator of life infuses that little body with a spirit. In other words, men and women dont create life God does. But, men and women do have the ability to put the process into motion. The question is: Do they have the right to take that first step without having first been given the divine approval to do so? I don't believe they do.
It might be argued that sex doesn't necessarily need to result in conception. And that's correct. But, I see the potential for procreation, and the concept that God has given human beings the right to be as co-creators of life as being so sacred that whether a child results or not makes no difference. The act is the same regardless.