General Douglas McArthur on “staying young”:
Youth is not a time of life, it is a state of mind.
Nobody grows old merely by living a number of years; people grow old by deserting their ideals.
Worry doubt, self-distrust fear and despair, these are the long, long years that bow your head and turn the growing spirit back to dust.
You are as young as your faith, as old as your doubt; as young as your hope, as old as your despair.
So long as your heart receives messages of beauty, cheer, courage, grandeur and power from the earth, from man, from the infinite so long are you young.
When the heart is covered with the snow of pessimism and the ice of cynicism then I am grown old indeed, and may you, Lord, have mercy on my soul.