When we become Christians, God forgives our every sin and grants us the gift of everlasting life. The cross paid for our crimes against His law and our case was dismissed. That’s the legal side. But experientially we are still tempted by the flirtatious pleasures of sin. Like a man who smokes 40 cigarettes a day has no problem with cigarettes until he tries to stop, so every Christian — particularly men — feels the power of the addiction of sexual lust as soon as he tries to stop. 

The hypocrite secretly gives himself to sexual imaginations, but the Christian knows that God sees his thoughts and considers lust to be adultery, (Matthew 5:27-28) and so he walks in continual and sincere repentance. The hypocrite lacks the fear of God, and dives into sin while the Christian falls into it against his will. The difference is huge.

Here is what frees the Christian from condemnation:  

Let the words of my mouth and the meditation of my heart be acceptable in Your sight, O Lord, my strength and my Redeemer. —Psalms 19:14 

Notice the word “meditation.” When a lustful thought comes to the mind of a Christian, it is what he does with it that determines whether or not it is offensive to a holy God. Does he meditate on it, chew it over and enjoy its mouthwatering pleasure, or does he spit the poison out through confession and repentance? It is up to us what we do with it and God’s wisdom.