"Don't grow up, grow forever!"
— anonymous
"Man must make his peace with his seasons, or the gods will laugh at him."
— Mary Renault
See the potential of youth, but also its shadow. As George Bernard Shaw said,
"The problem with youth is that it is wasted on the young."
Youth has its own natural glamour, charisma, and sparkly glow. In our culture, many biological, chronological adults are ungracefully aging adolescents, forever fighting a losing battle to appear young.
The problem is not with youth, but the unconscious overvaluation of it. Those who actually are biologically young are often the most aware that chronological youthfulness is not the magical answer to the human condition.
Even as I get ever older, I always seem to have many young friends due to mutual affinity related to a key aspect — inner dynamism. The young are more likely to have this quality, while many people stagnate and rigidify with age. But this is a general pattern with notable exceptions. Many young people have already lost their inner dynamism, and some older people retain it or may even be growing their inner dynamism. This dynamic and metamorphic quality, which a person of any chronological age could possess, is Youthfulness with a capital "Y."
A key aspect of Youthfulness is a connection to beginner's mind, and the imagination and creativity of the Magical Child and Eternal Youth archetypes. But you want access to these archetypes, not to be ruled by them. If they rule you, you may end up, like Michael Jackson, caught in Never Never Land, where you seek to stave off aging through plastic surgery and relating inappropriately to the young. (see the HBO documentary:
Leaving Neverland )
The fascination with youth pathologizes when we overvalue the temporary bodily form of youth and neglect the vitality of our inner self. However, accepting the inevitable aging of our corporeal body does not mean that we have to accept the typical premature aging associated with the standard American diet and sedentary lifestyle.
Exercise can help grow new brain cells at any age.
Your present age does not define who you are. Anyone who lives long enough goes through all the ages. We don't think of saplings and mature trees as different species; a sapling is a tree that has yet to mature, and one imagines that mature trees don't spend their time longing to be saplings again.
On the other hand, age denialism is a losing game. Age is not "just a number," it's a biological reality. Our bodies, like those of other animals, are pro-aging, and we do need to make peace with our seasons. We may have to relinquish the youthfulness of our bodies, but not necessarily the Youthfulness of our psyches.