“it’s crazy that none of us can afford to live in the town where we were kids,” said a high school classmate at a recent mini-reunion. We’d grown up in Concord and Carlisle in the ’80s and ’90s (when, we all agreed, “normal” people could still buy homes there), and many of our parents had attained the American Dream, as it’s often defined: earning more degrees, owning bigger houses, and generally leading more comfortable lives than their own parents had.

My family’s story was fairly typical. My mother’s parents fled Eastern Europe between the wars with nothing but a long-handled brass kettle. My mother grew up sleeping on the living-room sofa in a one-bedroom apartment, and then went on to earn a master’s degree, a job with a company car, and a suburban house with a swimming pool. My older brother and I, on the other hand — well, let’s just say we’ve got master’s degrees. (It’s possible that I have a kettle somewhere, too.)

My brother and I live in smaller spaces than our parents did at our age and pay a bigger percentage of our income toward housing. Census data show we’re not alone. In 2006, 49 percent of the renters in Massachusetts — a group that includes a lot of young people — paid more than 30 percent of their income toward housing. Given the rapid rise in the cost of homes, energy, and education, the dream of “doing better” than our Baby Boomer parents may no longer be realistic for middle-class young people in this state. But rather than feel as if we’re scrambling to keep up with the place where we started out — not a good recipe for happiness or optimism — it’s time to redefine what it means to do better. (For more on how young people in Massachusetts view their economic situation, and their future, see the new MassINC report Great Expectations: A Survey of Young Adults in Massachusetts.

Don’t worry: This won’t be a lecture about how heated garages aren’t necessary, 980 square feet is a perfectly livable amount of space, and success must come from within. Those are all true, of course. But the drive and insecurities that make us want to surpass our parents aren’t likely to go away. Although we gripe about Baby Boomers sucking dry the nation’s resources — goodbye, Social Security — our generation nonetheless seems to take a positive view of the future. We may be optimistic because we can’t wrap our heads around the reality that we will someday need those vanishing retirement benefits. But perhaps we anticipate success in our futures because at least some in our generation are beginning to think about success differently. Here are two new gauges I’ve noticed: flexibility and sustainability.)

Many of my friends place a high premium on job flexibility — and not just the ones who are raising kids. While my brother, a computer programmer with a 2-year-old and an infant, values his ability to work from home occasionally, a friend without a family sublets his apartment for the month of January and goes to a warm-weather place with his laptop. Another pal with relatives in Asia goes back and forth several times a year, sometimes without her employer knowing which continent she’s on. And I’m writing this column while sitting in a park.

Flexibility has its trade-offs. When you can work from anywhere, it’s easy to always be working. But the ability to control how and where we work may, increasingly, be a sign of having “made it.”

Another sign of having made it — one that conveniently fits our reduced buying power — is living a more sustainable lifestyle than the Baby Boomers did. In some social circles, green living has become an important status symbol, much in the way the three-car garage once was. One canvas grocery bag is hipper than 8 million plastic ones. Growing your own tomatoes is cooler than buying a crate load of them from Costco. The new owners of hybrid vehicles call friends to crow over their mileage miracles much as they call pals in New York to gloat whenever the Red Sox beat the Yankees.

Yes, some products are labeled “green” as a marketing ploy, and yes, many seem to cost twice as much simply because the g-word is stamped on them somewhere. But beyond the greenwashed marketing, some of us really are redefining what it means to live well: living in a way that will give our own kids cleaner water and air than we had, and will free up money for things other than gas, car insurance, and heating bills.

Perhaps we will reach the point where, instead of smugly comparing the size of our homes to our parents’, we’ll smugly compare fuel efficiencies. Instead of telling our children stories about walking uphill both ways to school in our bare feet, we can tell them about the bad old days when grandma and grandpa didn’t know any better than to leave the air-conditioning on even when nobody was home—and just how horrific the traffic on I-93 was once upon a time.

Given the limited size of our state, and the state of the planet, we can’t keep defining success in terms of More, Bigger, Shinier, and Newer. We need to look toward categories like flexibility and sustainability. At high school reunions everywhere, we should encourage each other to think in these terms.

Alison Lobron is a writer in Cambridge. She can be reached directly at alobron@hotmail.com.