How can a hardened heart that fears not God repent, and how can a person return to God after numerous sins and despair of receiving a response?

To overcome hardness of heart, one must cultivate the fear of Allah, while maintaining good thoughts about Him and never despairing of His mercy and forgiveness, no matter how great the sin. One should also persist in repentance and seeking forgiveness, strive in supplication, and adopt means of righteousness such as keeping good company, frequently engaging in remembrance (dhikr), reciting the Qur'an, and utilizing virtuous seasons, for Allah never turns away one who turns to Him.