What is the meaning of remorse, and how can a servant be sure that he is remorseful for what he has done? And what is the meaning of persistence in sin, and when is a servant considered persistent in it?

Regret is sorrow and remorse for sins committed, and the Prophet, peace and blessings be upon him, said: "Regret is repentance." As for persistence, it is the continuation of sin and not abandoning it. Allah has described the righteous as those who "did not persist in what they had done while they knew." A minor sin grows in magnitude through persistence. A servant is considered persistent if he does not abandon the sin and regret it. However, one who abandons and repents, then returns to it due to weakness, is not considered persistent.