Old people are the worst.

They're bifocal-wearing zombies shuffling toward cubicle hell; they laugh at things that aren't funny; they follow rules that don't make sense. Adults wear sweaters even when it's warm out. They do drugs — but only lame ones given to them by doctors. No more smoking weed.

So why grow up?

Well … we kind of aren't these days. Peter Pan is our national hero.

Michael Bywater noticed this in his book "Big Babies: Or, Why Can't We Just Grow Up?" He sounds like a grumpy old man who wants everyone to be grumpy, but he has points.

People go out of their way to take off their big boy pants and put on diapers — sometimes literally. In New York City, this happens a lot. "Grownups Pay Big Bucks to Attend NYC 'Adult Preschool'," says ABCNews. There's finger paint, and show and tell, and the only difference is that the grownups don't eat the Play-Doh — probably because Play-Doh has gluten in it. There's prom for grownups, where, if it's anything like actual prom, everyone drinks cheap liquor and has unsatisfying sex. And there's a "Skipping Club," a club where adults flitter and trot around New York City skipping and bouncing like schoolkids but with tattoos.

These were all designed to make adults feel more childlike. Which isn't all bad. But there's a difference between childlike and childish.

Being childlike is wondering at an orange sunset. Being childish is complaining that the sunset isn't orange enough. Being childlike is getting dirty playing in the mud. Being childish is pooping in your diaper and making other people change it.

We're childish now, un-grown. The world is full of beer-bellied, neck-bearded toddlers, waddling around with head down, eyes buried in their Candy Crush. Not calling people back, not paying child support, not contributing with a real job, not showing up to court or Thanksgiving or the town council meeting where they're voting to replace the aspen trees near the creek with a parking lot for a Dildo Store.

Staying childish feels like you're giving the middle finger to The Man — who is unfair, who never gave you a chance — by acting young, by not buying into their rules and their systems.

Lots of parts of adulthood are awful. But it's time to change the idea that all of growing up is awful. Susan Neiman, in her book, "Why Grow Up? — Subversive Thoughts for an Infantile Age," says that The Man wants you to stay childish, so he can sell you stuff to make you happy.

And she shows why growing up can make you happier than you ever thought possible.

First, she points out, being young isn't all that great. Teenagers are miserable more often than they're stoked. Prom was mostly awkward; your first few handjobs were torture; your first job was greasy and low-paid. In your 20s, you're often not in love, you can't find a career, you haven't figured out a job that doesn't suck your soul out through your pores.

It's true that lots of jobs suck; Neiman says that what worries teens isn't that they have to grow up and go to work, it's that there's no decent work to grow up for. "Fewer jobs than ever require energy, spirit, and the use our best capacities, honor and dignity; most involve doing things that are patently useless, possibly harmful, certainly wasteful and demeaning and dumb to boot," she writes.

Being an adult is rebellious. It's "subversive," writes Neiman. Subversive means: sneaky, undermining, and looking to fuck shit up.

Growing up can look different for everybody, but it's mostly about showing up. Standing up. Being visible. It means showing up as a parent, worker, soldier, sibling.

Growing up isn't so bad — especially when you choose how it is that you want to grow up. Take the fridge. If you're a grownup with your own money, you put whatever you want in the fridge. Every time you open it: there's your favorite stuff.

Here's another reason why growing up isn't so bad: legal weed. For a long time, we were told that smoking pot was just for kids to experiment with. At the same time, we were told that drinking alcohol was mature.

And a lot of stoners subtly went along with that. They smoked in the basement like disobedient children, while The Man profited on pilsner, prisons and pills.

Then, a few stoners grew up — and stood up. They went public — smoking in front of people, on front porches, on chair lifts. The bravest smoked before town council meetings, before going to ballot boxes, to regulatory commissions, before voting — and the law changed.

You see the sign on the outside of the pot stores, now?

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Adults, motherfuckers. Adults, one and all. Adults getting rich off weed. Adults getting happy. Adults getting lifted.

Cannabis legalization was a small revolution. But there have been others: gay rights, civil rights and sexual rights. And there will be more to come.

And, admit it, you want a revolution of your own.

Your revolution might be big: winning the whole Drug War, say, or crushing fascism or communism. It might be small: convincing your neighborhood to drop the speed limit so kids can play in the street again.

But you want that power.

You're not alone. While you might think it would be crotchety old men like Michael Bywater who appreciate "Why Grow up?", Neiman says she's gotten lots of thanks from readers under 30 who don't want to stay young, look young, think young, act young. They want the power that comes from being fully adult.