Do past sins continue to affect a young man who has repented from fornication and many other sins, and who suffers from obsessions that remind him of them even during prayer, knowing that he fasts for the sake of Allah?

Man is in a constant struggle with himself (nafs) and Satan. The intrusive thoughts (hawajis) come from both. The nafs is prone to evil, "except what my Lord has mercy upon," and poses a great danger if it is not fought with the reins of piety. Satan strives to mislead man by all means possible. The heart is like a fortress, and Satan is an enemy trying to enter it with whispers (waswas). One is not held accountable for intrusive thoughts as long as they are not spoken or acted upon. Sins and transgressions are the cause of every affliction in this world and punishment in the hereafter.