The Gemara says that a soul is brought to G-D before being sent down to
this world. It is given its attributes: whether the person will be smart
or not, rich or poor, etc. The one thing which is **not** decreed is
whether it will be good or evil. That is up to the person to make of
themselves. Each decision made in either direction (i.e. good or evil)
affects the goodness of the soul and makes the next step in the same
direction that much easier and the next step in the opposite direction that
much harder. But, in the final analysis, you don't get, either before
birth or during life, a better or worse soul; you are, so to speak,
solely responsible for how you turn out.
Gershon