If

"If you can keep your head when all about you
   Are losing theirs and blaming it on you,
If you can trust yourself when all men doubt you.
   But make allowance for their doubting too;...

Or watch the things you gave your life to, broken,
   And stoop and build 'em up with worn-out tools:...

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 your beginnings
   And never breathe a word about your loss; ..."
read Rudyard Kipling's full poem here