"The soul was sent down into this world to improve it. However, not only does it fail to improve the world, but it
does more damage than when it began. As a result it has to come back a second time, but this time under the duress of a more
difficult life challenge....
"The main thing [to keep in mind is
that the purpose of reincarnation] is to effect the repair of a [negative] influence originating in a previous lifetime... [One way] to discern exactly what that negative influence
is is to reflect upon the type of wrong your soul yearns after the most in this lifetime. That which you yearn after most
is likely something you became habituated to in a previous life. And therefore pay attention to your vices. [They tell you
exactly what you have to work on in this lifetime.]
"...The main thing is to repair that which one stumbled in in a previous [life] ... How can one know what one stumbled in in a previous life? ... [Pay attention] to that particular sin one’s soul longs for greatly
(for it was emblazened into the soul as a habit in the previous life). That’s why some people are drawn after one type
of sin more than another. And that’s also why our Sages say that one must continually judge himself and weigh his actions..."
(Vilna Gaon, Commentary on Jonah)