Sex is for the bonding of the spirits of a man and a woman. So, since God created it He sets the rules ( only for married men and women ). If you break the rules, that's between you and God. The reason that it hurts when people break up is because the spirit aches when it has to disconnect once connected, its very powerful. Sometimes its more powerful than the mind. Some lovers refuse to disconnect once bonded. It has been the cause of many a murder.