There is a famous story in which there are two factories on either side of a river. One factory takes big rocks and turns them into a fine powder. The fine powder is then shipped across the river to the other factory. The other factory takes the fine powder and makes from it rocks. The rocks are then shipped to the other factory and turned into fine powder. The process continues in a lifeless loop.
The story is, of course, meant to capture a certain feeling about the futility of modern life. That feeling is all too common, and a natural outgrowth of unbelief. If you do not believe in God, and if you are a thinker, you might begin to sense that all the arguments (economic, biological, psychological, etc) in the world don't give life much meaning.
And that is just the point: Life without God is truly meaningless. It doesn't matter what kind of mental acrobatics you try to perform -- you can't get purpose and meaning without God. So the unbeliever tries to forget his emptiness in the intensity of one momentary experience or another. This is the origin of sexual hedonism. (Incidentally, it is also the origin of the Cult of Now -- you know, those folks who bow before the idol of NOW. An idol that insists it is the only thing that exists.)
Funny thing about sexual hedonism (indeed all hedonism) is that it suffocates itself: the pursuit of sexual pleasure as an end in itself leads ultimately to boredom, cynicism, ennui, and finally despair.
Temporal pleasures, which are fleeting by nature, simply cannot satisfy the immortal soul. Trying to fill the void with sexual pleasure is like trying to quench the desert one teaspoon at a time. There is no better recipe for unhappiness!
Sexual hedonism is a perversion of the soul's demand for divine love. This perversion impels people to look for the infinite love of the Lord (though they do not know they look for it) in finite things. Some people follow this desperate road so far that they contemplate killing themselves -- a kind of last rebellion against God.