The correct attribution http://www.snopes.com/politics/quotes/carterpoor.asp is comedian John Fugelsang, on the TV program Viewpoint (29 May 2013)
Misattributed
http://groups.yahoo.com/group/cerebus/message/100634
“When you can stop you don't want to, and when you want to stop, you can't…”
Source: Candy
“You don't write because you want to say something, you write because you have something to say.”
Notebook E: Epigrams, Wisecracks, and Jokes https://books.google.com/books?id=NIhKY8SpAE4C&q=%22You%20don%27t%20write%20because%20you%20want%20to%20say%20something%3B%20you%20write%20because%20you%27ve%20got%20something%20to%20say.%22&pg=PA123#v=onepage, edited by Edmund Wilson (1945)
Quoted, The Crack-Up (1936)
“You don't want him for a reason. You want him because he's your father.”
As quoted in A Taste of Death: Thirty Days with U.G. in Gstaad, Switzerland http://www.scribd.com/doc/3101240/A-Taste-of-Death (1995) by Mahesh Bhatt. Bhatt precedes this quote with the observation "You are what you do, not what you say you want to do" which has sometimes been misquoted as part of Krishnamurti's statement.
