My nine-year-old daughter is an athlete—strong, muscular, coordinated, and fearless on a soccer field. She has clearly inherited the genes of her Chinese birth parents, who might have been Olympic gymnasts or divers. I, on the other hand, have my parents’ DNA, which gives me a 50 percent chance of being sporty. My father ran marathons and smashed tennis balls well into his seventies. My mother preferred activities like cooking, reading books, taking naps—going to the Y or for an afternoon walk only on occasion.

At 51, I am beginning to feel my age, and have become painfully aware of my physical limitations. There are days when my muscles ache and my joints hurt, days when I’d like nothing better than to join my 83-year-old mother for a catnap on the couch. But as a single parent of an athletic child, I feel bound by a sense of duty.

The other evening, for instance, Eleni stood at the front door, brandishing a large, electric-green rubber ball, a plastic baseball bat, and a Wiffle ball. “C’mon, Mom,” she said. “Let’s go out and play!” I knew there was no way to escape her entreaties, so we walked up the block to the park. For the next 90 minutes, Eleni put me through the paces, as we shot hoops, threw and kicked the ball around, and took turns swinging the bat. As twilight turned to darkness, I suggested we go home, and was relieved when she agreed.

Back in our apartment, I lay in bed, nearly immobilized (with ice packs on my feet). Eleni thought this was hilarious, and jumped on the mattress beside me, with tons of energy to spare. I lay there thinking that I wanted my daughter to be proud of her body, to believe that she can play any sport and be as physically tough as she wants. And I realized, too, that I’m not always an ideal role model.

Try as I might, I’ll never be the cool, young, athletic mom, or the devoted dad, like my own, who spent countless summer evenings playing catch in the backyard with his daughter. Most of the time, I’m just too tired!

When I adopted Eleni, nine years ago, I had no idea how the journey ahead would unfold. Now I can say that single motherhood has made me stronger, forcing me to dig deep and find a wellspring of resolve. It has also compelled me to face my limitations. As the sole parent to my little girl, I have come to see that there are things I do well (I often offer wise counsel) and things I don’t (I’m a hapless cook) and, somehow, I hope to split the difference.

So as to my daughter being an athlete, I try to offer support. I drag her to swimming classes on Wednesday afternoons, wake up early on Saturdays to take her to soccer games, and cheer mightily from the sidelines whenever she scores. I do my best to play sports with her and try to heed her advice (“Mom, you really need a pair of sneakers. You’d run a lot faster if you didn’t wear flip-flops.”). And I expose her to female sports stars on TV (“Wow, Mom! Maria Sharapova is so pretty!”).

Sometimes I wish I could do better. But time and again, my body reminds me that I’m 51 and she’s nine. That’s not a bad thing, by most accounts. But for the sake of my health—and safety—please don’t ask me to ride a skateboard or climb a tree!