By John Valentik, MS, CSCS, NASM-PES, CES

Tomorrow marks my 39th birthday—or my annual aging event, as one of my friends likes to say.

While anyone more than ten years older than me will probably chuckle, I’d be lying if I said I haven’t felt a little anxiety about entering the final year of my 30s.

Then I remind myself of something important: Whether you’re in your 30s, 40s, 50s, 60s, or beyond, you can continue to improve in the areas of life that matter most to you.

Success isn’t always linear. Progress doesn’t always happen on our preferred timeline. But there are still countless opportunities to grow, learn, and challenge ourselves regardless of the of our age.

Just two weeks ago, Paige and I completed a Half Ironman. It was the longest swim, longest bike ride, and longest duration of exercise I have ever accomplished in my life. Six weeks before that, I published my first book when, ten years prior, the longest thing I had ever written was a blog article.

Could I have done those things at 25? Maybe, but I didn’t. I did them at 38. Those experiences reminded me that growth doesn’t stop simply because we get older.

We also don’t need to measure every goal by a number. Sometimes we become so focused on pounds lost, dollars earned, miles run, or promotions received that we forget to ask a more important question:

Does this fill up my cup?

For those in their teens, 20s, and 30s, answering that question may feel a little easier because there seems to be so much runway ahead. You can still chase personal bests, change directions, and reinvent yourself if necessary.

Maybe your next goal is a Couch to 5K. Maybe it’s a marathon.

Maybe it’s starting a side business, buying your first home, learning a new skill, or finally taking that dream vacation you’ve been talking about for years.

Figure out what matters to you and work backward from there. For those who believe they’re “past their prime,” I’d challenge that idea. There are still countless opportunities to improve.

Maybe it’s picking up a new hobby. Maybe it’s improving your flexibility. Maybe it’s losing a few pounds that slowly found their way onto your frame over the winter months.

If you’re already settled into your career, perhaps growth looks less like climbing the ladder and more like improving your attitude, your leadership, or how you show up for the people around you.

Maybe success looks like spending more time with your family and less time at the office. Regardless of where you find yourself on the age spectrum, there are opportunities to continue getting better.

Old dogs can learn new tricks. In fact, one could argue that old dogs need those tricks more than the young pups.

Our brains are remarkably adaptable. Scientists refer to this as neuroplasticity—the brain’s ability to form and strengthen neural connections throughout life. When we challenge ourselves with new experiences, new skills, physical activity, meaningful relationships, and continued learning, we help keep those pathways active and engaged.

The alternative is autopilot. When we stop learning, growing, and challenging ourselves, we become more likely to repeat the same thoughts, behaviors, and routines without much intention.

So regardless of your age, regardless of your decade, think about the kind of person you want to become. Think about the people you want to surround yourself with. Then make sure your next action aligns with that vision.

Tomorrow, I turn 39. And while I may be getting older, I still plan on getting better.