When will a person be held accountable for his deeds, and does remembering past sins after repentance affect it, especially when there are those who know about those sins?

A heart that trembles before God is a sign of acceptance and favor, as stated in the Quran and Sunnah. However, this fear can turn into despair and despondency if a servant does not maintain a balance between fear and hope. This leads the servant to have a negative perception of God and to become lazy in worship, which is a new sin. Infallibility lies in adhering to the fear of God without falling into obsessive thoughts or frustration. The son of Adam is not held accountable for his sins until he reaches the age of puberty; what occurred before that is not subject to reckoning. If the sin occurs after puberty, a distinction must be made between praiseworthy fear and blameworthy fear that leads to despair and the abandonment of worship; otherwise, this blameworthy fear is considered a new sin related to one's perception of God.