The gem cannot be polished without friction nor man without trials. – Confucius

The rays of happiness, like those of light, are colorless when unbroken. – Henry Wadsworth Longfellow, Kavanagh, 1849

When you forget to take the sail at all, then the wind is constantly in your favour both ways. But there! this world is only a probation, and man was born to trouble as the sparks fly upward. – Jerome K. Jerome, Three Men in a Boat (To Say Nothing of the Dog), 1889