What if I did something forbidden (haram) in my teens, knowing it’s forbidden (haram), but because I had the idea in my head that everyone is doing it, so I did it. I kept on doing it until I realized it’s one of the greatest sins. I regret doing it and I know that God is merciful and God forgives the the greatest sins, but I still can’t get the idea that I have committed one of the greatest sins out of my head, which causes me to isolate myself from others and always see myself in life as a sinner.
Allah says in the Holy Quran:”(Muhammad), tell my servants who have committed injustice to themselves, ‘Do not despair of the mercy of God. God certainly forgives all sins. He is All-forgiving and All-merciful.'” [39:53]
One of the greatest gifts that Allah has given us is the gift of repenting and seeking forgiveness. Through sincere repentance, all of a person’s sins will be forgiven, even if they equate the number of the stars or are as heavy as the mountains.
Allah loves a person who sincerely repents for his sin; hence, the repented sin will be considered as if the person never had committed that sin. In Wasail al-Shia, v.16 p.74 Imam al-Baqir (p) said, “He who repents of his sins is as one who has no burden of sin.”