How can one quickly return to Allah? And does intense striving in worship soften the heart and hasten the return to Him, or does that require a long time, along with the fear that repentance may not be accepted?

A servant draws near to his Lord by striving in acts of obedience: by observing the obligatory duties, increasing in supererogatory acts, persisting in supplication and remembrance, and contemplating death and what comes after it. For whoever keeps knocking on the door will enter, and whoever draws near to Allah by a handspan, Allah draws near to him by an arm's length. As for repentance, its door is open, and its conditions are easy, and no sin is too great for Allah to forgive. Therefore, the servant must have a good opinion of his Lord and not despair.