Stop and think about the nature of forgiveness: each of us is capable of both giving and receiving it. But what about self-forgiveness?
This source from the Talmud gives us some insight into the importance of self-forgiveness.
ת"ר עבירות שהתודה עליהן יוה"כ זה לא יתודה עליהן יום הכפורים אחר ואם שנה בהן צריך להתודות יוה"כ אחר ואם לא שנה בהן וחזר והתודה עליהן עליו הכתוב אומר (משלי כו, יא) ככלב שב על קיאו כסיל שונה באולתו
With regard to transgressions that one confessed on this Yom Kippur, he should not confess them on another Yom Kippur, since he has already been forgiven ... And if he did not repeat them but did confess them again, about him the verse states: “As a dog that returns to its vomit, so is a fool who repeats his folly” (Proverbs 26:11), since it is inappropriate to go back and mention one’s earlier sins.
This shows us how strongly the sages believed in self-forgiveness. They even make the rather disgusting comparison that a person who repeatedly confesses to the same sin is like a to a dog returning to its vomit. If you have already been forgiven by God, then why haven’t you forgiven yourself?