When God created mankind, he created them male and female with the intention of them pairing up and becoming companions of a special kind. Each one would leave their family of origin and experience a oneness with each other that would be more intimate and permanent than with any other human they met. They would even have new titles: husband and wife.
To make sacred this oneness, and to aid them in having a relationship with each other that would be one of a kind, he gave them something called sexual desire. This desire in humans was designed to be controlled, saved, and then, Lord willing, unleashed and satisfied only within this one of kind relationship called marriage.
Sex is the one relational act that the husband and the wife would give only to each other, forever marking and celebrating their unique oneness. Even the fruits of pleasure and children were designed to deepen this oneness exhibited in marriage.
When sexual desire is used in any other way, for any other purpose, it is called sexual immorality, and the desire to use it in any other way is called lust. Lust is the sinful driver behind countless acts of sex of all kinds that disregard God and dishonor its object.
In this world, sexual immorality and lust are considered normal and human. In the church, sex within marriage is considered normal and human. God demands a sharp contrast, and therefore says, "Among you, there should not be even a hint of sexual immorality." (Ephesians 5:3)
May God help us to remove this death from our life.