Is it permissible for a person to intend, through supererogatory acts of worship, to reform their heart so that they may be able to be mindful of Allah and fear Him?

Good deeds are among the causes of guidance. There is no blame on whoever performs acts of obedience out of devotion and a desire for guidance, for Allah increases those who are guided in guidance, chooses for Himself whom He wills, and guides to Himself whoever turns to Him in devotion. And those who strive for Us – We will surely guide them to Our ways.