Dr. David Minkoff shares what he's learned from competing in multisport as a septuagenarian.

There’s one thing I want to get out of the way—I’m not unique.

Meeting someone who has finished multiple Ironman triathlons after the age of 70 may not be an everyday occurrence, but it’s not all that rare, either. There are quite a number of us, and then there are a few like Madonna Buder—the Iron Nun—who are in a league of their own.

But that doesn’t stop me from wanting to share my experience with you … or more importantly, the revelations it has brought me. So buckle up while I attempt to impart some “old man wisdom,” from a guy who’s completed 43 full Ironman triathlons and countless halves and who’s still going strong.

1. Your 70s are not your 30s… or your 40s.

“Age is just a number.”

“You’re only as old as you feel.”

At some point, these sayings start to break down, and a somewhat less forgiving reality emerges: There’s no deceiving your own body.

Acknowledging reality is crucial. It gives you the power to decide how you’re going to live within it. I’ve found that I can remain in peak shape, slowing down only slightly, versus the precipitous decline that we as a culture tend to associate with “aging.”

2. It’s more productive to ask, “How can I?” than it is to ask, “Can I?”

The latter is the question that comes to mind more readily, especially when faced with a new or unique challenge—but consigning yourself to the binary greatly limits what you can achieve.

I have learned how to ask, “How can I?” From there, a path of action inevitably reveals itself.

3. It was never about winning.

I might have disagreed with this statement earlier in my racing career. I probably believed that pushing myself and determination were about being as good as I could be. Maybe not beating the pack, but beating myself, in a sense.

But it’s really not about that. It’s about enjoyment. Even when joy hurts. In running, as in life, the cliches are ripe for the picking; but it’s true that in the end, it isn’t about the destination, but the journey.

4. You have to be in it for you.

Just because you’re crossing the finish line as a septuagenarian doesn’t mean people surround you to proclaim their congratulations. In fact, just because you succeed at anything against the odds doesn’t mean you’re going to get special treatment.

Whatever it is you’re going to do, you have to do it with the assumption that no one will notice at all. True satisfaction comes from within.

5. It’s okay to act your age.

I don’t want to say that I’ve learned to embrace being old. Nor do I want to act “old.” But I’ve learned to be okay with acting like I’m over 70 (because I am), and I’ve accepted that there’s nothing to prove. This is a concept I would’ve had a lot more trouble with when I first started competing.

6. Rest days are non-negotiable.

Really, don’t we all need a bit more rest? Surveys say that one-third of us are sleep-deprived. Maybe you can push through when you’re young or even when it comes to activities that aren’t so physically stressful.

At 70-plus, though, training becomes just as much about knowing when to stop as about knowing when to push it. I used to worry about doing too little. Now I avoid doing too much.

This is a lesson we should take with us everywhere. Working too hard is one of the most common regrets of the dying, according to hospice nurse Bronnie Ware. Whatever you’re doing, it’s okay to take a step back.

7. Getting older isn’t so bad.

In fact, it’s honestly not bad at all. Leaving aside the cliches about senior citizen discounts, aging does bring with it some added wisdom and a greater sense of appreciation in many aspects of life.

Like I think everyone does, I always had some “nervous butterflies” about what advanced decades would bring. As it turns out, I can still do almost everything I ever wanted—and more. I also care less what others think, so in a way I’m far freer than I ever have been.

And if I can compete in an Ironman triathlon at 71 years old, after all … what can’t I do? My future is bright.