When you’re an adult and alone in an unknown place, you don’t have the luxury of homesickness. There is no built-in solution. There is no dugout. There are no teammates, no roommates, no boot camp brethren. No shared experience to quickly overcome the hurdle of distance.

You can miss home indefinitely. You can be far beyond homesick and just be sick for home. There is a big difference.

If you’re lucky, there are emails. There are letters. There are phone calls. There are the occasional visitors. There are times when a part of your home shows up on your doorstep — literally or figuratively — and stays awhile. But it is fleeting.

No one really tells you this growing up. No one tells you that the very place you resisted for years and decades could be the very place that makes you physically ache at its thought once you’re hundreds or thousands of miles away.

There is a bigger unspoken secret, though. It’s that you don’t have to leave home to lose it. Home can leave you. One night, you fall asleep at home. The next night, you lie awake in bed in a different world. You can’t sleep. You can’t move. Life instantly becomes so foreign that you might as well be staring through the dark at a ceiling in Munich or Lima or Copenhagen.

This can happen with any major loss. You lose a job. A child goes to college. A loved one dies. Someone you love leaves and loses you.

And just like that, home is gone. Even though the walls still stand and the roof only feels like it’s caving in on you.

So what is home?

A city? A building? A person or people?

Driving home from a distance, a familiar skyline can spark warmth in your chest. The energy and heat intensify with a turn into a driveway. They threaten to explode as a door opens and a set of arms reaches wide to overtake your momentum, arms that stop you just so that they might have the satisfaction of pulling you inside, into your home.

Or so I’ve heard.

I know people who talk of home like this. Many people. This was not my home. Growing up, home was something that rarely crossed my mind, and I was something that rarely crossed its threshold. I was an original latchkey kid. I had parents who worked. I had friends and a bike. I had no desire to go home until I was fifteen minutes late.

As a senior in high school, I moved in with a friend who had a house to himself thanks to that friend’s mom who had a boyfriend with a house to himself and her. I never lived with my parents again.

In the six years that followed, I moved 19 times. The last was after my wedding and ironically took me back to my childhood home — as a rental tenant. There were three more houses in as many states over the next 15 years. Toward the end of that time, there was a ninth floor hotel room on an expense report in Santa Monica that felt more like home than the “matrimonial residence” (as the divorce decree would later call it) 1500 miles away. The only two things I wanted from that home were my kids.

Now I provide a home — an apartment, actually — for those kids five nights out of every two weeks. I occasionally ask them if it feels like home, just to make sure they have a sense of place. They assure me that it does and that they do. But it doesn’t feel like home to me. It feels like a place where I temporarily get to live with my girls. I’m incredibly grateful for that. I couldn’t ask for more, except to ask that it felt like home. But I wouldn’t know what that felt like.

To me, no physical space has ever felt like home.

I know someone who misses home.

She misses a city’s skyline and the things she knows witihin that city’s silhouette. The bars and bowling alleys and ballparks and city parks and coffee shops and churches. The old friends, the college friends, the work friends, the sports friends, the bar friends, the good friends, the bad friends. The trees and snow and lakes and streets. The family.

She can stand anywhere in that city and close her eyes and know that she’s home from just the sounds — of the insects and the traffic and the long Os of her Midwestern people talking to one another as they walk to the bar or the bowling alley or the church. Or just back to their homes.

When she speaks of home, there is reverence. There is also pain, because she is not there. Not often. Not often enough. Not every minute of every day.

It’s said that “Home is where the heart is.” For certain, her heart is there. But I don’t believe that’s all. I don’t believe that it’s just the heart, that the heart completely dictates home. My heart has traveled many miles and resided in many places, in many spaces. None of them felt like home.

Two weeks ago, I ran a twelve-hour trail race. In a timed race, there is no set distance. You run a trail loop over and over at your own pace. You run your race. The person next to you runs hers. In the end, someone has the most miles. Only a few of the 68 people who lined up at 7 a.m. on that Saturday were gunning for top mileage. None of those people were me.

I would have liked to have completed 50 miles. I didn’t. I was undertrained. I ran the last eight hours with a couple of damaged toes. And race day happened to fall on the hottest, most humid day of the year so far.

At the end of the 12-hour time limit, I’d run 39 miles. Tired, I stayed for just a few minutes at the post-race beer and pizza dinner. Then I drove home and rode my building’s elevator for the first time in three years, my legs unable to take the stairs. I half sat and half fell on the couch, opened my laptop and posted a summary of the race day on my Tumblr. Several people congratulated me. A few called me insane.

Then, one of my friends replied: “What are you running from?” Not long after, I got a text from another friend asking the same thing.

My brain doesn’t stop.

It’s not working to expand theories on quantum physics. It’s not solving problems of geopolitical strife. It’s usually just trying to get a shitty ‘80s song to quit playing on a constant loop in my head. Or it’s failing at prioritizing the hundreds of emails I owe to clients, coworkers, friends and relative strangers. Or it’s trying to decide between spending too much money on take out or spending too much time on cooking once I’m at my apartment. This usually results in my brain berating itself at midnight for the failure to decide, a non-decision that leads to me going another night without any dinner at all.

My brain’s real strength, however, is in creating worst-case scenarios. For why my kids haven’t returned my texts. For how a random closed-door office meeting between two members of the management team is obviously about my poor work performance. For why I’m to blame for a coworker’s bad mood. For the reasons why people I care about will eventually never speak to me again.

If you give my brain enough work and enough ADHD medication, the noise subsides. I can focus for large chunks of time with only minimal internal distractions. I can accomplish the necessities and occasionally capitalize on the opportunities. Once I stop focusing on the day’s work, however, the signal-to-noise ratio becomes imbalanced. By the time I get home, my brain is hosting a three-ring circus narrated by a perpetual internal monologue that wears a top hat and acts as ringmaster.

It only stops when I start running.

I’ve been running for less than four years.

Unlike many people, I didn’t take up running to lose weight. I took up running to gain strength. Some physical, mostly mental. I was emerging from the rubble left by the slow-motion implosion of my marriage. I needed to rebuild myself in many ways. There was a girl who was helping that process, most of the time from hundreds of miles away. She was a runner.

She was why I started running. She was not why I continued. At least not at first.

I’m actually well-known for not continuing anything. I throw myself into new hobbies and interests with all of my passion and most of my disposable income. Typically, the moment I accumulate all of the necessary equipment for an endeavor is the exact moment I get bored and find something shinier.

Running doesn’t take a lot of gear. Don’t get me wrong, you could spend the GNP of a Caribbean nation on running gear. Eventually, a lot of runners do. But to start, you just need some shoes. So I bought shoes.

During every run for the first few weeks, I thought about two things: how much everything hurt and how much I didn’t want to be running. For reasons I don’t remember, I didn’t quit.

One night, I started walking in order to cool down after completing my distance goal. I felt good. I actually felt great. And then I realized that I remembered almost nothing about that run. I had snapshots of digital numbers in my head from the times I checked my watch while I ran, but that was it. There was no mental movie of the run, no memorized transcripts of an internal monologue. I’d spent 30 or 45 minutes without thinking.

It felt loose and calm and comfortable. It felt like home.

For a long time, I used running as a reset button. Bad day at work? Run. Long, expensive phone call with my divorce attorney? Run. Condescending, accusatory email from my soon-to-be-ex? Run.

I was training for 5Ks and 10Ks. My longest runs were an hour. Most were less than 30 minutes. It’s all I needed — just a little reset on most days. I was settling into a new life. It wasn’t without stress. But I had a job, I had my girls, and I had the girl.

Then I lost the girl. And I was beginning to lose the job.

My brain went batshit. I couldn’t go more than a few minutes without the internal, anxious monologue overriding any productive thoughts. It was like unleashing Iggy Pop on the Partridge Family. The simplest tasks at work took hours for only passable results. On the nights that my girls were with their mom, I was alone and paralyzed on the couch.

My home became haunted with the ghosts of relationships and decisions and missed opportunities, so I laced up my shoes and ran out of the door every chance I got.

Running became different, though. I slowed my pace. I ran farther. I stayed on the trail longer. Anything to avoid unleashing my thoughts on my thoughts. Minutes became hours. The 6.2 miles of a 10K became a good start. I bought new shoes every three months. I bought a headlamp. I eventually bought a backpack that held two liters of water, four Clif bars and half a dozen gels. I was doing anything I could to avoid going back.

While I was running, I was safe. It became my home.

Eventually, thoughts of the girl subsided. I got another job. I moved on, but I’ve never stopped moving. The trail is still a place where I find shelter from my brain and its usually ridiculous worries. I’m still lacing up my shoes and walking out of the front door to find my way home.