Sarah Blakely didn't tell anyone of her billion-dollar idea for Spanx for a year.
1. Early on, she didn't want to spend time defending her idea to others.
2. She didn't want others' opinions - even for valid reasons, to sway her in seeing her idea through.
By her own admission, if she'd listened to others who told her that the big boys of industry would wipe out her $5000 life savings and steal her idea- which could've happened, she'd still be selling door to door today.
Instead, she kept her idea to herself and went to work.
Think about this...
If you keep your idea to yourself and don't tell anyone what you're working on for 365 days, a) it'll not only test your commitment (i.e. "Is it worth it?!) b) you won't back down to others' opinions when they rise and see your dream through.
The people who try to talk you out of your dreams are the very ones who gave up on theirs.