Another thought - a positive outlook probably has a much greater effect on the training that you are willing to do (again, motivation) than on your performance on a given workout or race. No amount of positive thinking will get you more watts when you don't have them. If visualizing a good result and how you're going to get it will help you focus on the right tactics for the best result possible, then I can see that helping in a limited way, but when the chips are down and you need the snot to bridge that gap or make it over that climb or sprint hard enough... well, when it comes to that, either you have it or you don't.