As the Earth spins inexorably forward, more elder millennials like me cross the great divide: We turn 40.

I was among the first of my generation, defined as those born between 1981 and 1996, to face the prospect of getting old, or at least being no longer young. What would it mean for us? Mortgage payments, pre-menopause, a midlife crisis — if we could even afford one?

When does midlife begin, anyway?

When I was in my late 30s, I took this question to the oldest person I knew: Shirley Hodes, my grandmother-in-law. She was then on the cusp of turning 105 in an assisted living facility outside Asheville, North Carolina.

Her answer delighted me: "I think 'middle-aged' is when you start collecting Social Security."

I laughed, thinking about how Suze Orman recommends waiting until you're 70 to begin collecting Social Security benefits, if you can. "So, even 50?" I asked. "Fifty is not 'middle-aged' yet?"

"Oh goodness, no!" she replied. "Absolutely not. At 50, you're just starting to live."

This strikes me as the mindset of champions. And your mental approach to aging can matter a surprising amount when it comes to wellbeing and longevity, studies indicate.

"There's a connection between mindsets and health behaviors," Eric S. Kim, a psychologist and researcher affiliated with Harvard University's Lee Kum Sheung Center for Health and Happiness, told the American Heart Association News in 2022.

Negative beliefs about aging can be "a self-fulfilling prophecy," while positive beliefs can prompt you to form and keep good longevity habits, said Kim. In other words, building and maintaining strong relationships, taking on new challenges, and figuring out how to cope with life's ups and downs can all help you live, and stay healthy, longer.

Your mindset doesn't guarantee longevity: Eating fresh, healthy foods, exercising and managing stress all matter. So does luck.

Still, it's important to "keep your sense of humor, give something of yourself to others, make friends who are younger than you, learn new things and have fun," Harvard Medical School psychiatry professor Dr. George E. Vaillant told the Harvard Gazette in 2001.

Hodes, who turned 108 this fall, is a great role model on this score. She's always loved books and theater, learning new things, and cultivating relationships. She worked full-time for about 20 years after her youngest child went to college. After retiring at age 70, she audited classes at her local college, camping out in the front row so she could see and hear everything.

When she moved into an assisted living facility, she made it her business to get to know the other residents. "It keeps me interested!" she told me last year. "I sit with new people, make conversation, ask questions, get them to open up."

No matter your age or your circumstances, she's told me more than once, "you have to concentrate on the positive."

Inspired by her vibrant example, I've decided to keep thinking of myself as young-ish for a while longer. Now that I know I'll just be starting to live when I hit 50, I have something great to look forward to.

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