As for sports, I've always liked running best. You don't need mounds of equipment. You don't have to wait for all the players to show up on the field to play. You can run anywhere, anytime. Back in high school, I ran cross-country for a few years. Some days we trained on rocky trails, others on steep hills or sprints. We ran—and got drenched in sweat—every day.

In college, I became a Sunday afternoon jogger. If I skipped a week, it didn't matter. On visits home, I'd run woodsy trails or lap the track, but never did more than three miles. When I joined the workaday world, I could only fit in occasional treadmill workouts when I'd push the speed to 7 and log four miles. That was long-distance to me then.

In October, I'll run my first marathon with my college roommate. I don't know what kind of journey I'm starting, but already my lifestyle has changed. The casual 30-block jog with my neighbor has turned into regularly covering Central Park's 6.2-mile loop. I started lacing up with a running club on Tuesdays and Thursdays and entering local races. I bought slick new sports bras and running shorts. I've started thinking of myself as a runner. Now, I run five days a week, sometimes more. I want to run farther, faster, and smarter. There is little else that makes me feel as free and confident, focused, and radiant as running does. I tie my shoes, pump up the volume and, like Nike advises, just do it.

Still, I've run 10 consecutive miles just once...and only recently. Rounding mile 6 nowadays, I think about adding 20. Some days, I wonder if I can really do this, if I'll be ready, what it feels like to hit the wall I've heard about, if I'll be strong enough to plow through it, and what it will be like to cross the finish line. My first marathon is 15 weeks from Sunday. Join me as the training begins. Let's do this!