I really like what Coach Wainwright stated in his post i think that all coaches have definitely dealt with or are dealing with this at some point in coaching. One poem i really like that i got from the book WRESTLING TOUGH by Mike Chapman is this:

If you think you are beaten you are;
If you think that you dare not, you don't;
If you'd like to win but you think you can't,
It's almost certain you won't.

If you think you'll lose, you've lost;
For out in the world you'll find
Success begins with a fellow's will.
It's all in the state of mind.

If you think you are outclassed, you are;
You've got to think high to rise;
You've go to be sure of yourself before
You can ever win a prize.

Life's battles don't always go
To the stronger or faster man;
But sooner or later the man who wins
Is the man who thinks he can!