The word lust means a passionate longing for something forbidden. Concupiscence adds the sexual connotation. Emotions are quite powerful when it comes to controlling behavior. However, until such a bond is consummated, there must be restraint place on such feelings. The strong emotion placed in man is meant to establish and maintain that durable bond in marriage.
Christians are to live a quiet life of hard work and endurance.
Jesus did give a difficult task of living in opposition to our natural instinct. But He gave methods to accomplish such a assignment. It is the idle mind that becomes consumed with passion. Therefore, one can avoid the enormous temptation of sexual immorality by being about the work assigned. He desires for Christians to grow in sanctification.