Source: The War of Art: Break Through the Blocks & Win Your Inner Creative Battles
“Success is blocked by concentrating on it and planning for it … Success is shy — it won't come out while you're watching.”
No known citation to Williams. Attributed in Quote Unquote (A Handbook of Quotations), 2005, MP Singh, Lotus Press.
The full quote is captured in a letter Tennessee wrote to Donald Windham and can be found on pages 57 and 58 of Tennessee WIlliams' Letters to Donald Windham. The quote is not misattributed.
Misattributed
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Tennessee Williams 139
American playwright 1911–1983Related quotes
“Plan for your success; Live your successio.”
Source: Life, the Truth, and Being Free (2010), p. 53

The Yoga Sutras of Patanjali, Book III, 2013
Context: Samyama, which is the application of concentration (dharana), meditation (dhyana), and superconscious trance (samadhi) in lightning succession, is practiced with the intent to gain specific knowledge of the object of concentration. The object is seen from all sides, in all its aspects, with full depth and breadth. As such, this complete absorption of the mind using the process of samyama brings complete and specific knowledge of the object. This power of knowing is vibhuti. (Bk. III, Sutra 4, p.7)

“If you don't tell people about your success, they probably won't know about it.”
Trump: How to Get Rich (2004), p. xiii
2000s

Is HP trying to be the new Apple? http://tgdaily.com/opinion-features/66609-is-hp-trying-to-be-the-new-apple in TG Daily (3 October 2012)

“Movies take years to bring to theater, but hours to watch. Strikingly similar to success.”

“People love you when you're successful, but if you're not, who really cares about you?”
As quoted in Boxing Monthly http://www.boxing-monthly.co.uk/content/0008/three.htm.
On his fans

Bloomberg Businessweek http://mobile.businessweek.com/articles/2013-03-07/africas-richest-man-aliko-dangote-is-just-getting-started