A philosopher once wrote, "There is not much to do but bury a man when the last of his dreams is dead." That seems to be the answer - a person is as young as his dreams - for it explains why some people are old at forty, others still young at ninety.
Youth is a time for tackling new projects, and as long as a person is enthusiastically beginning something new, he will remain young in the only places that really count, in his mind and heart. As Emerson said, "We need not count a man's years until he has nothing else to count."
The person who has no dreams to spur him on, no goal to achieve, is already old; for age comes when hope and planning for the future die. This is why a man's lifework must be much larger than an eight hour a day job. Men only grow old in occupation with fixed limitations, uninteresting surroundings, and with no call upon the imagination or the mind. But some men stay young, regardless of their work. These are the men who are striving for something better, something greater. People who stay young are people who feel young, regardless of their years. They are people who like to try new things and who like working toward a goal whether they live long enough to reach it or not.
People who stay young never think much about old age or death. They concern themselves less with what might lie beyond the pale and more with the here and now, with today and tomorrow and next week.
People who stay young keep their sense of humor; they know how to laugh, even when the joke happens to be on them. They do not hold grudges; if they are angered by something of someone, they are quick to forgive and forget. They seem to know that hatred hurts only the hater.
People who stay young look for and are quick to accept new ideas. They have a healthy curiosity about everything that comes within the range of their senses. They know that while they may slow down considerably from a physical standpoint, the mind can grow more able, more powerful with the years. A person can be at his best, mentally, even when he is at his eighties or even older.
But above all, they continue in pursuit of a dream, something to earn or bring about, a new, higher plateau upon which to stand. Titian was painting masterpieces when he was ninety-eight.
What is the dream you are trying to bring into fulfillment? A person is as young as his dreams and as old as his doubts.