If all of a human being's affairs are predestined and written by Allah, then why is he punished for his mistakes?

Man is an agent by his own choice. God's prior knowledge of his state and destiny does not mean that he is compelled. Man is punished for his shortcomings in this world and the hereafter because he acts by his own choice and will. If appealing to destiny were acceptable, man would refrain from necessary actions such as eating and drinking. Lifting accountability from the perpetrator on the pretext of destiny would turn life into chaos, and obliging man to absolute patience and non-objection to injustice is unbearable. This confirms that Islam has made man a free agent and responsible for his actions.