You will benefit when you tell lots of people your give up goals. Tell your friends when you want to give up overeating or binging or being a boor. Your friends will make it ever more difficult for you to feel good about backsliding.
On the other hand, the traditional wisdom is that you should tell very few people about your go up goals. Don't tell them you intend to get a promotion, win the race or be elected prom king. That's because even your friends get jealous, or insecure on your behalf, or afraid of the change your change will bring.
Here's the thing: If that's the case, you need better friends.
A common trait among successful people is that they have friends who expect them to move on up.
All credits for this to Seth Godin.