The destiny of a person is connected not only with those things he himself creates and does, but also with what happens to the soul in its previous incarnations.
The encounters and events of life, its joys and sorrows, are influenced by one's previous existence.
One's existence is a continuity, the sustaining of a certain fundamental essence.
And certain elements may rise to the surface which do not seem to belong to the present, which a person has to complete or fix or correct–a portion of the world it is his task to put right in order for him to raise his soul to its proper level.
–Rabbi Adin Steinsaltz
From The Thirteen Petalled Rose by Rabbi Adin Steinsaltz