My sins haunt
You might say: “I committed many sins, and I have repented, but my sins pursue me and I am haunted by what I have done. My memories disturb my sleep and do not let me have any rest. How can I free myself?”
My advice to you is that these feelings are evidence of your sincere repentance. This is essentially remorse, and remorse is repentance. But you can look at your past with hope: the hope that Allaah will forgive you. Do not despair of the mercy of Allaah, for He says (interpretation of the meaning): “And who despairs of the Mercy of his Lord except those who are astray?” [al-Hijr 15:56]
Ibn Mas’ood (may Allaah be pleased with him) said: “The gravest of major sins are to associate partners with Allaah, to feel secure against the plan of Allaah and to despair of the mercy of Allaah. (Reported by ‘Abd al-Razzaaq and classed as saheeh by al-Haythami and Ibn Katheer).
In the process of moving towards Allaah, the believer is always motivated by both fear of Allaah and hope of His mercy. One or other of them may prevail at times of need. If he sins, the fear of Allaah overwhelms him, and so he repents. When he repents, the hope of Allaah’s mercy fills his heart and he seeks the forgiveness of Allaah.