[dreeves]

Sivers later clarified that it's only true for "identity goals" where telling people about the goal is part of what the goal is. Like "I want to be a runner." By saying so you're making it sort of more true in that you're identifying as at least a wannabe runner.

I believe that for specific, discipline-oriented goals -- like "I want to run 3 times a week" -- you're well advised to shout it from the rooftops, as common sense would dictate.

Sivers's clarification, along with his original TED talk: http://sivers.org/zipit2