An interesting article which says that if you announce your plans you are less motivated to achieve them. Agreed. I have experienced the same thing myself.From the article:
Announcing your plans to others satisfies your self-identity just enough that you’re less motivated to do the hard work needed.
It may seem unnatural to keep your intentions and plans private, but try it. If you do tell a friend, make sure not to say it as a satisfaction (“I’ve joined a gym and bought running shoes. I’m going to do it!”), but as dissatisfaction (“I want to lose 20 pounds, so kick my ass if I don’t, OK?”)