Clinical psychologist Meg Jay recently gave a TED talk that may make 30-somethings or almost-30-somethings break out in a nervous sweat. Here’s her main message: You know how you’re always hearing that 30 is the new 20? Phew, right? Wrong!

According to Jay, 30 is NOT the new 20, and saying it’s so is a big problem. She frequently hears clients in their twenties talk as if things don’t matter: This relationship isn’t great, but I’m just killing time. I’ll just bartend for now and as long as I figure out a career by the time I’m 30, it’s fine. But it’s not. When those clients are about to hit 30, they change their tune: I’ve got nothing to show for my twenties. What was I doing? What was I thinking? Uh. Oh.

Here are a few reasons your twenties DO matter, according to Jay:
* 80 percent of life’s most defining moments take place by age 35.
* The first 10 years of your career has an exponential impact on how much you’ll earn.
* Over half of Americans are with their future partner by 30.
* The brain has its second and last growth spurt in your 20s.
Scared yet? Me too. But breathe easy: Jay has three tips she thinks every 20-something can benefit from hearing:

1. “Forget about having an identity crisis; get some identity capital.” By this she means, do something that adds value to who you are. Exploring new opportunities is great, but only if they count. Otherwise, you’re just procrastinating.

2. “The urban tribe is overrated.” Friends are great, but your “weak ties”—friends of friends of friends—are where the opportunities are going to come from. Expand your circle.

3 . “The time to start picking your family is now.” Jay says that the best time to start working on your marriage is before you have one. You don’t have to be married by 25, but stop wasting time and look for what you want now.

Got it? OK. Are you feeling terrified, or energized? I walked away from listening to the talk with equal reactions of fear (did I mess up my entire twenties), inspiration (cool, I can do those three things), and skepticism (is this even a valid theory?). All three reactions probably have a little truth to them.

I agree with Jay that your twenties shouldn’t be about wasting time—although a little fun is good, right?—and I think she makes a lot of great points about what a person should be doing to work toward the life she wants while she’s young. But I’m also glad that at age 29, I still felt young enough to be able to walk away from a career I hated and start a new one, even though it came with some sacrifices. Those of you who are familiar with me from over on Smitten know that before joining the Glamour.com team, I was a lawyer. I wasn’t “killing time” with it; I just came to realize it wasn’t for me, and so I made a change. I got some new identity capital. I think Jay would be behind that, and I don’t think she would necessarily criticize someone who did what I did.

However, part of the reason I had the privilege to take such action is because of the very idea that 30 is the new 20. When my mom was about to turn 30, she had a husband, two kids, a mortgage, and a job in the field she’d stay in her whole life. I had exactly none of those things. Sometimes that makes me feel like a failure, but more and more, I realize how much freedom not rushing into those things has actually given me to work toward the life I want instead of staying stuck in the one I happened to have at the end of my twenties. (FYI: I don’t meant to imply my mom was stuck in a miserable life. I think she’d say she’s happy with hers. But not everyone in her generation—or mine, for that matter—was so lucky.)

So, are 20-somethings today just wasting their time, or is there a bigger picture here that’s actually beneficial? It’s not to say there’s no room for criticism of today’s young adults, but I also don’t think an entire generation decided they could just do whatever they felt for an entire decade. For one, there are circumstances that lead us to feel “less adult” and the older generations to treat us as such.

A recent economic crisis means that many 20-somethings are financially insecure and less likely to be able to achieve that marker of the American dream, a home purchase, at least not in their twenties. We’re getting married older, yet our society continues to treat marriage as a major milestone of adulthood, meaning that an entire population of single 30-somethings is treated like kids because they haven’t yet thrown a black-tie dinner for 300. No offense to marriage, which seems awesome and I’d like to do it one day, but it’s not the only way for a person to become an adult. For two, I would venture to guess that a lot of 20-somethings aren’t intentionally wasting their time, but if they take some wrong turns in that decade, they’re relieved to know that’s not the end for them.

So maybe 30 isn’t the new 20. I, for one, certainly don’t want to be drinking the cheap keg beer and wearing the ratty boot-cut jeans I was in my twenties. And like Jay, I don’t want to see a lot of 20-something women thinking that these years don’t count. They count for a lot, and we should all make the most of them. But 30 isn’t what it used to be either—and that can be a good thing.