How can one forget a married woman he was speaking with, and how can he completely stop thinking about her, knowing that he tried to cut off the relationship but she still comes to his mind?

It is recommended to supplicate, show resolve, be sincere with Allah, completely close the door to Satan, and appreciate the blessing of lawful marriage and the seriousness of transgressing against the honor of others, along with repenting from slandering her and supplicating against her and her children.