Lust and fantasizing about someone
Jesus taught that lust is a matter of the heart, not just outward action: 'whosoever looketh on a woman to lust after her hath committed adultery with her already in his heart' (Matthew 5:28). Fantasizing about someone you are not married to takes a good desire God created and directs it outside his design. This is not about shame; it is about the heart.
Job made a covenant with his eyes not to look lustfully (Job 31:1). The way forward is honesty with God, renewing your mind (Romans 12:2), taking every thought captive (2 Corinthians 10:5), and replacing the pattern rather than only fighting it. God offers grace, not condemnation, to those who come to him (Romans 8:1).
If it feels compulsive, consider confiding in a trusted, mature believer (James 5:16).
From Bible Navigator's study library. Scripture quotations are from the King James Version (public domain). This is encouragement for study and reflection, not professional counseling - if you are in crisis, call or text 988.