One favourite poem is by A Schweitzer for aging concerns:
Remain Young
Nobody get old simply because he or she has been getting on in years. People get old as soon as they wave their ideals good-bye. As we get older, our skin gets wrinkly; however, if we stop being enthusiastic, our soul will get wrinkly too. Worries, Doubts, a lack of self-confidence, fear, and hopelessness, all of these are present throughout the long, long years, forcing the head down to the ground and bending the upright spirit until it touches the dust.
You are as young as your confident optimism, as old as you doubts, as young as your hopes, as old as your dejection. As long as the message of the beauty, the joy, the boldness, the greatness, and the might of the earth, and of humanity and the infinite realism are touching your heart, you will remain young. You will have truly begun to age when your wings are beginning to point downward and the core of your hear till be covered by the snow of pessimism and the ice of cynicism.