I've been in racing for 30 years and...wait, let me put my teeth back in. Ok. As I was saying, I've been in racing for 30 years, and I think one of the highest and best purposes of a coach is to teach a kid how to prepare mentally to race.
We all have so many doubts - if a guy knows how to inspire a runner- well, that's at least half the battle.
Watch videos of Joe Newton talking - I think there are some on Dyestat. A good coach has a way of making you believe you can excel and not fold.
Otherwise, everyone develops mental tricks to get over mental doubts. I just tell myself before a big race that I'll just tempo it. Then the competitive fires kick in and I'm off.
Apparently boys need to feel they are not letting down their team. Girls have a more self-centered motivation. Or at least I read that somewhere.