I am searching for a particular quote by Helen Keller that includes
some version of the following: "a person with disabilities will never
know/discover their hidden resource of strength until they are treated
like a human being and encouraged to shape his or her own life".

The quote is:

"A person who is severely impaired never knows his hidden sources of
strength until he is treated like a normal human being and encouraged
to shape his own mind."

The quote is present at the top of the Arc Nature Coast website:
http://www.thearc-naturecoast.org/customer%20services.html

And on this quote page: http://www.viguide.com/lighterside.htm#Quotes

Google results for the quote:
://www.google.com/search?q=%22+A+person+who+is+severely+impaired+never+knows+his+hidden+sources+of+strength+until+he+is+treated+like+a+normal+human+being+and+encouraged+to+shape+his+own+life.%22&num=20&hl=en&lr=&ie=UTF-8&c2coff=1&safe=off&filter=0

Hope this helped. If you need more information or my answer is not
exactly what you are looking for, please feel free to request a
clarification.

Thank you so much! I needed this to place on a dedication plaque and
wanted it to be accurate!!