“Substitution” is a well known psychological effect: when you announce your goals to people, you receive psychological satisfaction, and it makes it less likely you achieve them. See this TED talk and related Fittit post. If you walk around telling friends “I’m going to lose 80 lbs”, this makes it less likely you will lose it. If you must tell them something, tell them what you’ve already done: “I have lost 10 lbs” but don’t talk about your goal (although you should certainly have one).
For additional reading check out Stop Telling People Your Goals which cites this paper.