How can one achieve sincere repentance and devotion in prayer after succumbing to sins and heedlessness, while fearing a return to them, and how can one get rid of the whispers of Satan?

Allah takes responsibility for pardoning and forgiving sins, no matter how great, for those who repent with a complete repentance that fulfills its conditions: immediately ceasing the sin, feeling remorse, resolving never to return to it, and restoring rights to their owners if they pertain to other people. It is recommended to increase good deeds, such as: supererogatory prayers, fasting, remembrance of Allah, reciting the Quran, keeping company with righteous women, and reflecting on the lives of the Mothers of the Believers; all to strengthen faith and feel happiness and tranquility.