The Only Sin That Harms Its Doer
Imām Ibn Taimiyyah, may Allāh have mercy on him, said:
The sin that brings harm to its doer is the one for which no repentance has occurred; as for that for which repentance has occurred, then its doer may [well] be better after the repentance than he was before the wrong.
Majmūʿ Al-Fatāwá, vol. 15, p. 54.