How can I distance myself from the forbidden with conviction and be guided by Allah, when I am in a relationship with someone I want to leave but cannot?

The way to avoid the unlawful is to be certain that it is a pleasure of an hour and a torment of an age, and disgrace and shame in this world and the Hereafter, unless Allah grants repentance to its perpetrator. The unlawful causes distress, torment, and misery, whereas obedience and chastity bring happiness. Allah the Almighty said: "Then if there comes to you guidance from Me, then whoever follows My guidance will neither go astray nor suffer. And whoever turns away from My remembrance - indeed, he will have a difficult life, and We will gather him on the Day of Resurrection blind."