Optimism

Optimism is such an important thing in everything I've ever done, and I've struggled a lot to shrug off my natural pessimism. I've had a lot of races where I finished far below my potential because I simply didn't believe I could do well, or found myself higher up then expected, and simply failed to believe I was actually supposed to be there, and therefor failed to capitalize on making that lead group.
Negative prophecies always come true. If you think "I'm going to bonk halfway through this" then you will. If you think "I'm going to win by 20 minutes", you won't, but at least it's better then thinking failure. The trick is to be realistically optimistic. Training is not just about trying not only to make yourself faster and stronger through actually doing physical activity, but through training your brain, making yourself believe that the training is working. That is one of the great things about comparing how fast you were previously to now. Because unless you think your training is working, it won't. You can train all you want, but if you don't think, don't say "I'm getting faster, I'm getting stronger, I'll be better this season then I was before", you won't be.