Rudyard Kipling's words come to mind:

If you can make one heap of all your winnings,

And risk it on one turn of pitch-and-toss,

And lose, and start again at the beginning

And never breathe a word about your loss;

If you can force your heart and nerve and sinew,

To serve your turn long after they are gone,

And so hold on when there is nothing in you,

Except the Will which says to them: 'Hold on!'

Yours is the Earth and everything that's in it,

And - which is more - you'll be a Man, my son!