You are as young as your self-confidence, as old as your fears; as young as your hope, as old as your despair.
Nobody grows old merely by living a number of years. We grow old by deserting our ideals. Years may wrinkle the skin, but to give up enthusiasm wrinkles the soul.
Maturity is the ability to think, speak and act your feelings within the bounds of dignity. The measure of your maturity is how spiritual you become during the midst of your frustrations.