What is the ruling on being attached to a man who is not one's fiancé, while still having a past love for him and not forgetting him or replacing him with the fiancé?

The relationship of love between young men and women is not approved by Islamic law, nor is it acceptable according to Islamic morals. If an emotional attachment occurs without pursuing forbidden means, the legitimate path is marriage. If marriage is not possible, then both parties must disengage from this attachment. It is obligatory for you to turn away from this man as long as marriage to him is not feasible, and to occupy yourself with what benefits you in your religious and worldly affairs. If your fiancé is a man of good character and religious commitment, then it is preferable that you accept him. However, if you see that married life with him may not be stable, there is no harm in breaking off the engagement. You can also ask the one you love to propose to you, if he is a man of good character and religious commitment.