The man who views the world at 50 the same as he did at 20 has wasted 30 years of his life.

More from Muhammad Ali

• Grass grows, birds fly, waves pound the sand. I beat people up.
• He who is not courageous enough to take risks will accomplish nothing in life.
• Service to others is the rent you pay for your room here on earth.
• The man who has no imagination has no wings.