Almost every person bears the legacy of previous existences.
Generally one does not obtain the previous self again, for the soul manifests itself in different circumstances and in different situations.
What is more, some souls are compounded of more than one single former person and share parts of a number of persons.
A great soul is most usually reincarnated not in one single body but branches out, participating in a number of people, each of whom have to satisfy different aspects of existence.
In spite of this incalculable complexity, the soul will be made up of the same constituent elements and will have to complete those uncompleted tasks left over from the previous cycle.
Therefore 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