Where did we get the idea that youth is the best time of your life? Having failed to create societies that our young want to grow into, we idealise the stages of youth. Growing up has come to be viewed as a matter of renouncing your hopes and dreams, accepting the limits of the reality you’ve been given, and resigning yourself to a life that will be more boring and less significant than you supposed when you began it. Increasingly, grownups appear not merely sad but pathetic.

Consider the difference between JM Barrie’s Peter Pan and Steven Spielberg’s reworking for the movie Hook. Barrie’s grownups are dull but menacing, occasionally wistful; Spielberg’s grownups are ridiculous, not only ill-equipped for the adventures of Neverland but barely fit to live at all. Given the lack of compelling role models of adults in western media, it’s no wonder that Peter Pan is seen as a figure of rebellion, or that a great writer’s fondest wish for his newborn is that the child may stay for ever young.

Outside of fairy tales, no one remains a child for ever. For this reason the time of life most often idealised is the decade between 18 and 28, when young men’s muscles and young women’s skin are at their most blooming. Yet few people who are in or past that decade would choose to repeat it. For most of us, it’s a time of doubt and fear – that every decision is irrevocably fateful, that everyone else is more confident and capable, and above all that we aren’t sufficiently enjoying what we’re told is the best time of our lives.

Empirical evidence confirms what honest introspection knows: most people are happier after reaching middle age. Though there are variations in the global low point – the Swiss reach it at 35, while Ukrainians don’t hit rock bottom until 62 – all report becoming steadily happier after that. Researchers controlled all of the obvious factors, such as income, employment and family status, and found they didn’t matter: from the US to Zimbabwe, the evidence that life is not a downhill path is constant.

What explains the consensus on something so clearly false? An answer can be found where we might least expect it, in the work of Immanuel Kant. His famous essay What is Enlightenment? describes humankind’s exit from its self-imposed immaturity. Growing up isn’t bad, but it isn’t easy either. Laziness and fear lead us to acquiesce: it’s much easier to let others think for us.

Growing up, like enlightenment, is as much a matter of courage as of knowledge. Kant’s call to have the courage to use your own reason is well known, but few have heeded the warning that comes after it: no government has an interest in cultivating adults. It is far simpler to care for distracted consumers than to satisfy the demands of self-confident citizens.

So most of us spend our working lives making or marketing products developed to divert us. The things that capture our attention are never depicted as toys but as tools that are crucial for being adult. Bewildered by the choice when purchasing a smartphone, we easily forget how many decisions are out of our hands. Or did you choose to live in a world where oil companies can wreck the planet, governments spend more on weapons than on education, and children starve every minute for want of food others throw away?

Grownups take on questions that determine real lives, knowing they will never succeed entirely but refusing to succumb to dogma or despair. Both are surely tempting, and successfully resisting them is key to growing up. Not permanent youth but genuine adulthood is a subversive ideal.

There is reason to suspect those who tell the young to savour the best years of their lives. The tone is cheery, but the message is ominous: everything else will get worse. Thus young people are prepared to expect – and to demand – very little.

No conspiracy theories are necessary: we often collude in our own infantilisation, as we often join in with the curious derision that greets the news that an ageing rock star has reached a round-numbered birthday or opened a concert or gone on tour. Isn’t it time these people accepted their obsolescence and left the stage to others?

This sort of disdain and mockery is all the more puzzling since the recent concerts of Bob Dylan, Bruce Springsteen and Leonard Cohen were anything but laughable. Among others, these artists have shown how far and for how long human and creative development can continue, surviving flops and falls and excess and error – thus providing some models of growing up for which we can be grateful.