I believe the quote is "Whether you think you can or can't you're probably right". I tried this with my Olympic soccer team and found the players who didn't believe in them selves were the one who usually did poorly. After the first week of training I asked each one individually how they thought they did. To their supprise I then asked what I could do to help them achieve their goal and improve enough to make the team. Everyday after the regular training session we stayed and worked on what they felt they needed. The skill level went up margionally, the mental aspect went up a huge amount. They just needed to know someone believed in them.