At some point, the marathon will move beyond the physical capacity of your body or training. You will enter a really tough, hard-to-define area where your ability to continue moving is what separates you from the competition, what allows you to achieve the goals you set before you started.

While the miles pass incrementally, fatigue sets in exponentially. Mile 13.1 is not, I repeat not, the 'real' halfway point of the race. Almost everyone feels great at this point. Mile 18 is where things start to get serious, and every mile after that point is twice as hard as the one before: Mile 19 is twice as hard as Mile 18. Mile 20 is twice as hard as Mile 19, but also four times harder than Mile 18. You get the idea!

Since we don't enter this space in our training, it pays to have a clear 'One Thing' or reason to keep you moving when your body starts to push back. Maybe you want to finish before a certain time or pace group. Maybe you are planning on a great post race party. Maybe you are running in the memory of a loved one or to support a charitable organization. Whatever the reason is that you have, know that reason and have it ready to go at a moment's notice!

'Everyone is an athlete,' wrote the late George Sheehan, running's physician-philosopher. 'The only difference is that some of us are in training, and some are not.' Lifelong runners are in lifelong training. For us, the cliche has become the rule: Running isn't a sport, it's a lifestyle. At a certain point, running stops being about PRs, victories, or new highs in training volume. It becomes a part of who we are. It becomes something our bodies can do, rather than something we do to our bodies.

It fascinates me that nonrunners so often seem to think that running long distances must be intolerably boring. 'What do you think about when you're running?' they ask. That question has occasionally been explained as a fundamental difference between what experienced runners do when racing or engaging in training runs expressly intended to practice racing conditions, and the more easygoing runs people do just for fitness or fun, or to build a base to prepare their bodies for more ambitious workouts weeks later. When racing, the runner is like an airplane pilot who is fully engaged in monitoring and adjusting the controls. In this so-called associative mode, the runner is monitoring and adjusting his breathing, heart rate, core temperature, hydration, perspiration, tempo, gait, available energy, electrolyte level, nutrient intake, flirtation with anaerobic or lactate threshold, and of course the conditions of his ambient environment: air temperature and humidity, precipitation, wind velocity and direction, and terrain, all while anticipating the road ahead. Some of it is done subconsciously and some with deep attentiveness. On a more easygoing (or dissociative) run, he might think about his work or family, or replay a recent conversation in his head, or imagine what he'd like to have said in that conversation --or he might notice the wildlife around him with the same appreciation he would when going for a walk in Rock Creek Park or a hike in Yellowstone, or he might chat with a running partner about whether the Cubs will ever win the World Series. That's what runners think about on a long run: sometimes a continuous stream of data about the running itself, and other times a stream of anything from profundity to trivia about whatever.

If you've never raced a 5K -- I mean really truly raced one -- here's an experiment you can do right now to get an idea of what it's like: Hold your breath for as long as you possibly can... and then when you can't hold it any longer, hold it for another 30 seconds.

Kids have the best running style. It's not smooth. Not graceful. But there is a classification for their kind of gait. It's called, 'Happy!'

Running is a way of life for me, just like brushing my teeth. If I don't run for a few days, I feel as if something's been stolen from me.

Failure is as exciting to watch as success, provided the effort is absolutely genuine and complete. But the spectators fail to understand – and how can they know – the mental agony through which an athlete must pass before he can give his maximum effort. And how rarely, if he is built as I am, he can give it.

There is nothing quite so gentle, deep, and irrational as our running—and nothing quite so savage, and so wild.

This, then, is the pull of Boston, a chance to drink from the same deep cup of history as every great marathoner who has come before, every great champion who has run on exactly these same streets, whose dreams similarly have come true or been dashed over the daunting distance. The roads that make up the Boston Marathon hold the ghosts which define the sport and which unite all runners in a community of suffering and triumph. Name, if you can, another such event in any other sport.

People today are generally taught to wallow in the wake of little injustices done to them, to look for excuses to under-perform, to assign blame for failures and for failure to try. This cultural mind-set has infected running.

We demand recognition for doing something we should be doing for its own sake, because it is natural and good. We demand recognition even if we train haphazardly and race half-heartedly. We strive not to be the best we can be but merely to be. That's enough. We'll get by doing as little as we can and then demand some recognition for it.

And in the process we cheat ourselves. We never move far enough ahead in our training to hit that overdrive gear in our running, where the reality of a hard asphalt surface beneath our feet is negated, and we are floating, running strong and free like the human animal whose divine design infuses all of us. A result of our under-striving is that we never earn admission to that special place in our running where the joy of effortless movement resides.

Running has taught me that we are capable of doing more than we ever imagined, that we can overcome huge obstacles, and that consistency pays off!

Isn't it great that our sport doesn't need human judges? No need for us to worry about 'artistic' merit, no one around taking off points for our form. All we've got to do is just put low numbers on the objective, non-partisan, incorruptible clock. Best is least.

Any long relationship has its ups and downs. And for me, that hot honeymoon period lasted a really long time — what a trip we had! Running isn't so much a courtship at this point. I feel like I've become one with it. That being said, the romance hasn't died so much as it has become routine. Expected. Comfortable. Easy in its own way.

Of course I could train harder to gain speed or try longer distances to add more notches to my bragging belt — anything to spice up the known and shake up my motivation. Thing is, this post isn't about gaining motivation or smashing through plateaus. I think there's something to be said to settling into a good, healthy routine and being happy, fulfilled regardless of pace or whatever else I used to gain from lacing up at different events.

For a while, I questioned it. I searched for 'the answer' to rekindle my passion back to its previous levels. In the end, I am at peace with my current state of non-competitive forward movement as it nurtures my body and spirit. There's a calmness and confidence I have in my own athletic ability that I've never experienced before. And, though it sometimes feels odd, it's actually a great place to be.

Yet we all hold out hope that on this Patriots' Day the stars will align for us—my body will respond to all the hard training I've done, Mother Nature will hear my heartfelt pleas, I'll put together the race of my dreams. In this way, preparing for a marathon is a bit like planning for a miracle.

The marathon is the essence of the unknown transforming into the known; there's always as much potential for destruction as there is creativity, as much chance of misery as there is elation, as much room for heartbreak as there is for triumph. That's the fun of racing a marathon. It's about seeing if you can go to the very edge without going over the cliff.

All top international athletes wake up in the morning feeling tired and go to bed feeling very tired. —Brendan Foster, British distance runner and former world record holder

I love this quote because it humanizes elite runners to everyday runners. People think that we are superhuman, but when I am in full training, I am tired ALL of the time.

That's one of the great pleasures of an ultramarathon. You can hurt more than you ever thought possible, then continue until you discover that hurting isn't that big a deal.

And with each sprint, I strive to take as much pain as I can before I am forced to slow down.

It is not pain I seek. Pain is simply the symptom of lactic acid accumulating in my muscles, and I have to teach my body to handle lactic acid in races. You could as much say that I like lactic acid as suggest I like pain. 

Pain is to be used. At times, it warns me I am doing something wrong. At other times, it signals I am doing right.

If I am driving for the finish of a race and there is no pain, I know I have not yet pushed my body to its absolute limit. On the other hand, there is pain that commands to go this fast and no faster.

The runner is not a masochist. The runner does not enjoy pain. But between the runner and a personal best lies pain in quantity, both in training and in the race. And the pain, once endured, comes to have a value of its own. I do not seek suffering, but once it has been experienced, I feel somehow the better for it.

I'm really resistant to this focus we have on speed. If you do a 3:59 marathon you're awesome, but if you do four hours, you suck. Humans are not fast, we are not speed creatures.

Ironman. It's not about metal. It's about mettle.

You don't stop running because you get old. You get old because you stop running.