What is remarkable is that one can be a perfect saint and still have past sins that have not been taken care of. And also that we see from the sages that repentance does not finish the job.

A man marries a woman on condition he is a perfect saint, even if he is a perfect רשע evil person, she is married because of a doubt that he might have been thinking to repent. So we see if in fact he had been thinking of repenting then she is certainly married. From this we learn repentance is accepting on one's self not to repeat one's evil deeds.
But that does not make up for past deeds as the Gemara says repentance on a איסור עשה (positive command) works. Repentance on a לא תעשה [negative command] helps and the Day of Atonement finishes. Repentance on לא תעשה שיש בו כרת [negative command with cutting off] Repentance and the day of Atonement hep and pains and problems finish.But for חילול השם you need and three and then the day of death finishes the atonement.
What is remarkable is that one can be a perfect saint and still have past sins that have not been taken care of. And also that we see from the sages that repentance does not finish the job.

[This I think is not well known and even when I learned the Gates of Repentance of R. Yona I think I did not get the idea.]