Eight months ago when I announced I was going to run 30 miles on my 30th birthday to a friend she asked how long I could currently run. I chocked out 2.5 through my laughter over the absurdity of my dream. My running experience was a slow, shaky 2.5 mile loop that I did around my neighborhood when the weather was nice which, living in Eastern Massachusetts, was just about never. Still, I was determined to train for and eventually run the 30 miles.

With just under a month to go I’ve slowly worked my way up to running 25 miles. I’m still in awe that this is happening, that my body has somehow withstood hours of foot to pavement momentum.

Although I’m still reluctant to call myself a runner (I haven’t yet decided if I’ll continue jogging after the 50K haul), I have learned a thing or two about this crazy and exhilarating exercise.

1. Not all marathon runners look like supermodels

My earliest up-close experience with marathon runners came when I worked for a major bookstore in Boston as an undergraduate. Each year I watched the runners flow in after receiving their numbers in the nearby convention center to pick up books and magazines about the art that they had seemingly already mastered. I looked on enviously at their thin legs whose thighs didn’t touch at the top, their toned arms, and what I was sure was a six pack hiding beneath their new blue and yellow apparel.

At some point after the years of watching marathon coverage on TV and selling books, I began to believe that all marathon runners were as thin and lithe as the winners who graced the podiums post-race or the women who spent race weekends buying books.

Once, one of my high school students interrupted class to ask me if I could dunk a basketball. When his classmate told him there was no way I could jump high enough to reach the net, he defended me by saying, “Look at her calves man. They’re huge!” He held his hands apart to demonstrate their girth, indicating that I practically had watermelons tied above my shins.

Though I definitely did not get into marathon running so that I’d look like a supermodel, I did expect some sort of visible physical transformation to take place somewhere between mile 2.5 and mile 25. Rather than whittling my legs down to supermodel sticks, running has only made my calves rounder and my thighs thicker (lucky some other kind soul created an anti-friction balm that works amazing for women whose thighs touch at the top.)

The truth is marathon runners come in all body shapes and sizes.

2. Runners walk (yes, even during races)

I know, this one was the hardest for me to accept too.

As my mileage began to build beyond 10 and I abandoned treadmill running for the streets, I found myself taking walking breaks much more often than I would have liked to admit. There were times, especially when going uphill, that my watermelon calves felt as if they’d just been slammed by Gallagher’s mallet and walking seemed the only logical way to ease the cramping.

Early in my training I’d read an article that a man who had won the Boston Marathon had walked through all of the water stations. It was notably one man, one year, but still, he won. I decided that if he could walk a few feet every few miles, so could I.

3. It’s okay to “eat on the run”

My “on the run” protein and electrolyte choices.

When my trainer (who completed several 100 mile ultra-marathons) told me that she would hide small food packages along the trail before her run, I thought the idea was crazy. I thought eating on the run (literally) would lead to stomach stabbing cramping that would cut my race short.

When I returned home after my first 15 mile run and devoured a loaf of bread coated in half a jar of peanut butter because I was so famished, I decided to take her advice and pack small, easy to digest snacks. I found that carrying several fruit and nut protein bars and taking small bites during walking breaks helps me refuel and keep running.

4. Running is natural, but that doesn’t mean you’re doing it naturally

When I first started running more regularly in the fall my knees loudly voiced their dissent: IT band issues, popping, locking, barely being able to walk down stairs, feeling like I had the joints of an 80 year old woman for a week after a long run. I was determined though to make 30 miles a reality and so I began researching pain-free running.

When I ran track in high school I suffered severe shin splints that I iced and pretended weren’t as bad as they were. Having been a serious ballet dancer for years, I ran naturally by touching down the ball of my foot first, then lowering the heel. Turns out this led to the searing pain in my shins. When I learned this I concentrated my efforts on running heel toe, which brought on the knee trouble.

The most helpful article about running form that I read suggested running barefoot for a short length to discover your natural stride. Wearing shoes causes us to disrupt the way of running that naturally works best for our bodies, but that doesn’t mean you have to go barefoot forever. Run barefoot for a short while and you’ll probably discover that you land somewhere mid-foot so that the weight of your body is evenly distributed and doesn’t send jolts of tension up through your legs and into your back. If you can recreate this step while in sneakers you’ll notice a marked difference.

5. Anyone can be a marathon runner

Click photo to make a donation to the National Kidney Foundation.

As cliche as it may sound, I truly believe that if you set your mind to something, you will make it happen. This marathon run for me has been no different. When I returned home from my recent run that was set to be 23 miles and discovered that after a few wrong turns I had actually run 24.65 miles I was in disbelief. Four months ago five miles was a major milestone.

The key to training for a marathon, and really anything in life, is to start where you are. If you have absolutely no experience running you can’t expect to rise off the couch and complete a 5K within a day. Start with a mile and include frequent walking breaks. Stick with it until you can complete a mile without stopping, then slowly build.

The glue that I think has held me together through all of the training, no matter how long and exhausting the runs became, was my purpose. I’ll be running 30 miles on my 30th birthday to raise awareness for chronic illness and to raise money for the National Kidney Foundation (visit my Crowdrise page here to make a donation). I think that if I were just running 30 miles for bragging rights, I would have given up miles ago.

However long or short the race is you want to run, or whether you’re embarking on something else as grueling as a marathon, set an intention that speaks to you and gives you purpose and you’ll find it that much easier to keep going.