A story about 2 marketing scouts who to go to Africa to look at the prospects of selling shoes. The first marketeer sends an e-mail back to HQ saying "It's hopeless, no one wears shoes".
The second marketeer sends an e-mail saying "Fantastic, you won't believe it what a fantastic opportunity this is....no one has any shoes !

Both factually right...successful companies foster the positive by allowing people to put forward ideas with no fear of being ridiculed. People do suffer doubt, and doubt brings fear. Fear and belief compete for your minds attention. To ensure belief prospers in your team then demonstrate that you will allow people to learn from mistakes. It is no good telling people that they can make mistakes....what do your actions demonstrate? That will be what you are judged upon...