Youth is not entirely a time of life — it is a state of mind. It is not wholly a matter of ripe cheeks, red lips, or supple knees. It is a temper of will, a quality of the imagination, a vigor of the emotions.
Nobody grows old merely by living a number of years. People grow old only by deserting their ideals. You are as young as your faith, as old as your doubt; as young as your self-confidence, as old as your fears; as young as your hope, as old as your despair.
In the central place of every heart, there is a recording chamber; so long as it receives messages of beauty and hope, cheer and courage, you are young.
When the wires are all down and your heart is covered with the snows of pessimism and the ice of cynicism, then and only then have you grown old.