Positive thinking and affirmations are a great beginning to get you on
a more positive path in life.  A Course in Miracles is an
especially great book for helping you to begin this new life. 
Many people find, however, that this course is simply not
enough.  After completing the course over the period of one year,
they find that they want to start again and go through it another year
or even more. The important thing to recognize is that positive
thinking is only the beginning of a larger and more comprehensive
spiritual path.  It requires positive energy to undertake a
spiritual course because overcoming challenges takes effort and
strength.  As you gain energy, you will naturally call up greater
and greater challenges for confrontation.
People who suffer from low self image or negative thinking often carry
with them a core idea that they are a "victim" of the world and they
feel that they have somehow been cheated.  They point their
finger at others in order to feel better about themselves.  The
use of positive self affirmations is a great way to overcome this
victim kind of thinking but it is only the beginning.  These
affirmations and positive patterns of thought can sometimes be misused
as a way of asserting ourselves against an "imaginary enemy". 
This turning of ourselves against the negativity of the world can
merely strengthen the illusion that there is something out there that
is negative and worth fighting against.  Nothing could be further
from the truth. Negativity, in and of itself is nothing.  It does
not have an independent existence but is really better thought of as a
simple lack of positive thinking.  Moving beyond the duality of
Positive and negative is what it means to move "beyond positive
thinking" . There is nothing out there that is trying to hurt us. This
idea has been stuck in our minds and is part of an illusion that
merely needs to be let go of rather than "battled".  Using
positive thinking as weapon or a tool is not the way that self
affirmations were meant to be used....

Affirmations goal setting motivation & personal growth :
http://groups.google.com/group/affirmationsap