The difference between top class athletes and world class athletes is mostly mental isn't it? It's that additional 1%. You train your body to surf, so why not your mind too? I know for a fact that I'm a better surfer when I feel confident, fit etc. If a little doubt creeps in, I'm slower to my feet, I don't paddle as hard and generally have a bad surf. It's no secret that Kelly rates his mind as way more important that his body for surfing, and that guy has won a dozen world titles, he's the oldest and youngest world title winner, he's won more events than anyone else....do you need more proof that it's mind over matter?
In terms of NLP, it's an interesting debate. I've done a bit of this stuff with work, and whilst I'm far from convinced it's a science, I do think it can help improve confidence, self awareness, communication and things like that. I'd also argue that a lot of it is common sense.
From personal experience, I can vouch for visualisation working. When I was coming back from a knee injury a while ago, I was really struggling to get my front foot right underneath me, so I started imagining what I wanted to do as I stood up. It worked!
There, now where do I put my 2p?