From Andrew Carnegie in his autobiography:
I think my optimistic nature, my ability to shed trouble and to laugh through life, making "all my ducks swans," as friends say I do, must have been inherited from this delightful old masquerading grandfather whose name I am proud to bear. A sunny disposition is worth more than fortune. Young people should know that it can be cultivated; that the mind like the body can be moved from the shade into sunshine. Let us move it then. Laugh trouble away if possible, and one usually can if he be anything of a philosopher, provided that self-reproach comes not from his own wrongdoing. That always remains. There is no washing out of these "damned spots." The judge within sits in the supreme court and can never be cheated. Hence the grand rule of life which Burns gives:
"Thine own reproach alone do fear."
This motto adopted early in life has been more to me than all the sermons I ever heard.
Related previous post: Charlie Munger on cheerfulness