There are very few doctors who will ever look you in the eye and tell you that you really—really—need to run a marathon. It’s just not one of those things medical folk see as “good for the body.” And sure, the abuse you put yourself through in running 26.2 miles is not quite what the body was designed for. It’s the challenge, and the mental and emotional thrill of completing it, that leaves many marathoners in the bizarre position of chanting the “never again” mantra through the hours of the run, only to sit, beer in hand and medal around neck later that night and think, “again.”

But there is something to be said about training for a marathon. For me, having a goal—and the associated paralyzing fear of not being ready—was always an excellent motivator that got me out the door for a run rather than simply sitting on the couch. I like schedules and I enjoy the feeling of crossing off my daily mileage, knowing I’m doing what I need to be doing to be ready for an event months in the future.

And that—the physical and the mental—is the medicine. It’s good for me. It helps me feel more energetic, happier, and even more creative. (You cannot underestimate the value of long-distance running for sweeping through the less-traveled corners of your brain for old scraps of ideas and new inspirations)

The odd challenge for me was becoming a Dad. All at once, I was overwhelmed, exhausted, and far less likely to make time for myself. It was all about my daughter. And yet, at the same time, never before had I felt such a profound sense of responsibility in being healthy—not for me, but for her. I would sit in the chair in her nursery late at night, rocking her, and think to myself, I must do everything I can do NOW to make sure I’m here for as much of her life as I possibly can. I want to be healthy, strong, and happy—for her.

So I’ve seen more doctors in the last two years than I did in the previous decade. I’ve gone for the colonoscopy, and gotten reading glasses. I’ve opted for the flu shot and the whooping cough vaccine. This week, I’ll experience a night wired up in a sleep lab after talking to my ear, nose and throat doc about my persistent allergies, congestion, and—according to my wife—strange snoring that shakes me awake at night. I’ve had a CT scan to check the deep reaches of my usually inflamed sinus.

I’ve had a full-body skin cancer check and I’ve had a mole carved off (all clear). I’ve had blood drawn and my prostate checked.

And with every appointment, I’ve felt like I was being a good Dad. At one point, a doctor told me with the firmest possible tone of voice, that I must run. It wasn’t a suggestion, it was a prescription. She told me exercise was medicine—as powerful in fighting depression as an anti-depressant. She told me it wasn’t an option for me, it was an order.

And so having my goal of running my first marathon since the birth of my daughter fits right in with my overall mission of being the kind of Dad I want to be: healthy, happy, and sticking around to see my daughter grow up (and also be there at Walt Disney World in January to cheer me on when I run).