The Tzaddik falls seven times and rises. Why does the [Righteous] Tzaddik undergo reincarnation? [as opposed to the Sinner who is given three reincarnations, three chances to right his wrongs, before he is instead purified in Gehenom.] The Tzaddik lowers himself [eg. is reincarnated] in order to raise up those who thought of repentance but never acted on it.
(End of Tikkun 32, Tikkunei Zohar)