Does failing to meet the conditions for repentance—such as remorse and the resolve not to return [to sin]—affect the acceptance of prayer?

He who abandoned prayer and then became diligent in observing it but does not regret abandoning it in the past has not repented of this grave sin and remains exposed to the threat [of punishment]. As for the prayers he performs, they are valid and sufficient if they fulfill the conditions and pillars. However, he may be deprived of their reward due to his persistence in that grave sin and his lack of regret for it, as sins can nullify good deeds if the servant does not repent from them.