In the main book of the Kabbalah we read that those who are "the highest of all—those who can turn darkness into light and bitterness into sweetness—are those who enter by the higher gates."
Achievements of this magnitude bear witness of a high degree of repentance: the transformation of the past is complete, the sign of inversion perfect.
Consequently, whenever you turn your attention to somebody's life, to the history of a people or a religion, do not content yourself with asking forgiveness for the evil you may have done.
This is not repentance; this is not what is required of you.
Instead, you should regard the faults as something constructive, like the beginning of a new and beautiful story.
Put more succinctly, come to grips not with your failing but with your past that gave birth to it.
–Rabbi Adin Steinsaltz
From an essay, "Teshuvah" by Rabbi Adin Steinsaltz