If you devote your life to helping others, you'll stay young.

Buddhism Day by Day

Wisdom for Modern Life by Daisaku Ikeda
Monday, February 4, 2013:

 

You mustn't allow yourselves to grow old before your time. Please live with a youthful spirit. That is what Buddhism teaches us to do, and it is how life ought to be lived. If you make a commitment to work for the sake of others, you will be rejuvenated. If you devote your life to helping others, you'll stay young. The power of Nam-myoho-renge-kyo guarantees that.