Motivational Quotes

You can't go this far and not go farther. - Homer Simpson

I saw this one on someone's signature here on BT and I use it myself a lot as well as saying it to my kids when they are complaining about having to go to soccer/volleyball/baseball/track practice:

"There are two times to train, when you want to and when you don't"

Or something very close to that...

HTFU 

one of freckleface's siglines comes to mind,

"Beware the lollipop of mediocrity: lick it once & you'll suck forever"

When things go wrong as they sometimes will,
When the road you're trudging seems all uphill,
When the funds are low, and the debts are high,
And you want to smile, but you have to sigh,

When care is pressing you down a bit,
Rest if you must, but don't you quit.
Life is queer with its twists and turns,
As everyone of us sometimes learns,

And many a failure turns about,
When he might have won had he stuck it out.
Don't give up though the pace seems slow,
You might succeed with another blow.

Success is failure turned inside out,
The silver tint of the clouds of doubt,
And you never can tell how close you are,
It may be near when it seems so far.

So stick to the fight when you're hardest hit,
It's when things seem worse, that you must not quit.

“The future has several names. For the weak, it is the impossible. For the fainthearted, it is the unknown. For the thoughtful and valiant, it is the ideal.”
- Victor Hugo

or...

“Impossible is just a big word thrown around by small men who find it easier to live in the world they've been given than to explore the power they have to change it. Impossible is not a fact. It's an opinion. Impossible is not a declaration. It's a dare. Impossible is potential. Impossible is temporary. Impossible is nothing.”-Muhammad Ali

or...

"Excellence is caring more than others think wise; risking more than others think safe. Dreaming more than others think is practical and expecting more than others think is possible."

I've actually got a whole list.

Discipline is what makes punishment unnecessary. 

Things may come to those who wait, but only things left by those who hustle - Abraham Lincoln

when i want to take a break, i ponder the gentle words spoken by one of the best motivational speakers i've ever heard. 
"you're going to end up eating a steady diet of government cheese, and living in a van down by the river!"   -  matt foley

From my race reports: 

The more I push my limitations, the more I realize I don't have as many of them as I thought.

If someone beats me because they are better, I can accept it.  However, being beaten by someone because I am being lazy is not acceptable.