I just turned 39 last month. Thirty-nine is not a nice, round number. A person’s 39th isn’t traditionally considered a “milestone” birthday. You don’t see Hallmark cards or mylar balloons with a giant “39” on the front.

When you’re 39, nobody puts up funny signs with poems on them like they do when you’re 40. You know: “Lordy, lordy, so-and-so is 40.” What would it be for 39? “It’s fine. It’s fine. Karen is 39.”

See? Nobody wants to see a 39 sign in your yard.

You don’t even get to rhyme with “nifty” the way 50-year-olds do. I’m so jealous.

I figure, though, when you have myeloma, every birthday is a milestone birthday.

I decided I was going to mark my 39th birthday by participating in something called the Heartland 39.3 Series. This is a series of three half marathons, a total of 39.3 miles, run over four weeks in April and May in the Kansas City area.

When I signed up for this last September, it seemed like a great idea. It seemed like maybe the most fab­u­lous idea ever.

When April rolled around and I actually had to show up at these races and run 39.3 miles, it seemed, well, slightly less fab­u­lous. I think “insane” is a better word than “fab­u­lous.”

Somewhere along the way, I’d forgotten why I’d signed up, and I started getting cranky.

The day of the first race was freakishly hot and muggy for April, something I was unprepared for after training in winter temperatures. I started way too fast in the heat, hit the wall around mile eight, and did a slow run-walk (but mostly walk) the rest of the way, all the time grumbling to myself about how this was the worst thing that could ever happen to anyone – ever, ever, ever! – in the entire history of the world.

I get a little dramatic when I’m tired.

I felt much better at the second race, but around mile five, the sky turned black. Around mile seven, the heav­ens opened wide. I ran the next four-ish miles through a blinding thunderstorm, slogging through puddles that went up over my ankles.

The final race was about an hour from my house, so I had to get up extra early. I was losing enthusiasm for the 39.3 series, and for turning 39 in general. I was up at 4:30 a.m., moving around my darkened kitchen, putting together a nice breakfast of carbs, wondering again why I was doing this.

I absentmindedly reached under the waistband of my running skirt to scratch an itch on my lower back, and my finger felt a small, raised bump on my skin.

It was a scar from one of my bone marrow biopsies.

Oh, yeah. The cancer.

That’s when I remembered that scar was why I was doing this. Because it’s really exciting that I’m healthy enough to run 39.3 miles. It’s exciting that I’ve made it all the way to 39, and I’m incredibly optimistic that I’ll make it to 49 and beyond.

The 30-year-old who got that biopsy scar figured turning 39 was a distant dream. She could never, ever have imagined running 39.3 miles to celebrate.

Feeling that scar just then was a sign from the universe. Thanks to the universe, I was back in business, and I had a good race.

There were even desserts at the finish line. Happy birthday to me!

I hear so many people my age complaining about aging, saying how “depressed” they’ll be when they hit 40. Not me. A year from now, maybe I won’t be running 40 miles, but I will be celebrating big time. And I will be grateful.