You succeed, and then feel like a champion.
If champions are winners, then you rush to keep on winning.
You fail, and feel like you have let down yourself and others.
It hurts so bad, that you stop trying.
The end result, whether you win or lose, causes a lot of stress.
So how does one overcome it?
If you believe that all is in the hand of G-d, then no matter what you will be OK.
When you succeed, you do not rush for the next win, but thank G-d for the blessing he bestowed you.
And when you lose, you know that it was not a loss, but never meant to be.
That is the power of faith.