Most people just need someone who believe in them for them to excel. When someone says that he/she will do something, I really do believe they will do it. From experience, far the majority won't keep their word. It always will frustrate me deeply that they are unwilling to keep their word, and live as trusted people.
However the few people who actually put actions behind their words will benefit greatly from your belief in them. It is those people that matters, and it is why I say you need to believe in people.