This is one of my favorite quotes about the power of what we think about.

If You Think You Are Beaten

If you think you are beaten, you are;
If you think you dare not, you don’t;
If you’d like to win, but think you can’t,
It’s almost a cinch you won’t.
If you think you’ll lose, you’re lost,
For out in the word we find
Success begins with a fellow’s will,
It’s all in the state of mind.

If you think you’re outcasted, you are;
You’ve got to think high to rise.
You’ve got 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 soon or late the man who wins
Is the man who thinks he can.

–Walter D. Wintle.

How does our mental attitude and what we think about reflect who we are?