I wish to know to whom to i should attribute the quote: "You will
encounter no greater adversary than your own potential." and, if that
is the exact wording.

Dear toadrogue-ga,

I have used three of the main search engines and the Amazon.com search
engine in this research. I can only find one reference to the quote
you provided.
"You will encounter no greater adversary than your own potential."
://www.google.com/search?hl=en&lr=&safe=off&q=%22You+will+encounter+no+greater+adversary+than+your+own+potential%22&btnG=Search

I did, however, find a similar quote which I think may be the one you are seeking. 

"To fulfill your potential. You will never come up against a greater
adversary than your own potential, my young friend."
From Star Trek: The Next Generation, ?Evolution?, Season 3,
25/09/1989, by Michael Piller & Michael Wagner. Character, Paul Stubbs
to Wesley Crusher.

This is from a script which appears on an amateur interest web site.
(I cannot confirm if it is an accurate or genuine script).
 
"Scene 30
STUBBS
To fulfill your potential.  
(Looking inward)
You will never come up against
a greater adversary than your own
potential, my young friend."
http://www.st-minutiae.com/academy/literature329/150.txt
http://www.st-minutiae.com/

Also appears on this quote site.
http://www.quotegarden.com/self-discovery.html

Summary of the episode appears here.
http://www.totse.com/en/ego/science_fiction/tngs3.html

Incidentally, I did try other wording such as ?no greater enemy than
your own potential? without a great success.

I hope this answers your question. If it does not, or the answer is
unclear, then please ask for clarification of this research before
rating the answer. I shall respond to the clarification request as
soon as I receive it.
Thank you
answerfinder

Search strategy
?adversary than your own potential?

Very complete.....great references. This helps immensley as I need a
proper citation for a work in progress. Thank you.

Blessings, toadrogue