Everyone breaks at some point. There's a moment - maybe just a small one - when you're convinced you can't go on. Get me a helicopter. Or just a tent. I'm not moving any further.
About 4100 metres above sea level, with the goal in sight through the thin Andean air, I broke.
Your breath comes short up there, wheezing through your throat. There's just not enough oxygen - it's like being in the desert and trickling the smallest drops of water into your mouth. You gasp for more but it's not there.
Gradually, inexorably, I shut down, my swinging arms and plodding feet coming to a halt, dead still in the middle of the track. I looked up. So close, yet so far. "Just leave me here, guys," I heaved, hands on knees. "I'll see you at the top."
The others slowly wheeled around. Matt, my friend and hiking companion, looked mildly concerned but clearly wasn't standing for it. "No way mate," he said, berating me like a drill sergeant. "We're in this together. We're finishing this together. Come on, walk!"
I sighed. I gasped. And I walked. A single pace at a time - one small step for a man, one giant leap for my failing willpower. The highest pass on the Inca Trail was only 100 metres higher but it could have been hundreds of kilometres away.
"This better be worth it," I mumbled to myself.
The Inca Trail: it's one of those ultimate bucket-list destinations. It's rare you'll meet a traveller who doesn't have a goal to hike to Machu Picchu tucked deep in the recesses of their mind.
It's got it all: ancient history, incredible scenery, a sense of adventure and a challenge.
That challenge is to make it through. It's not a long hike, the traditional trail, but it's a tough one. It's the altitude that's the real killer - that and all those steep climbs to the passes. It's three days of solid plodding, one foot in front of the other, trying to remember to enjoy yourself as your muscles atrophy and your will to go on slowly seeps away. OK, that's a slight exaggeration but it still makes you question the sanity of anyone who'd want to climb mountains for a living. Or, geez, for fun.
The local porters don't seem to mind. They're truly incredible, in fact, the way they hoik huge packs onto their shoulders and literally run the trail, padding past you in leather sandals as they push it to set up camp and provide trekkers with another hearty meal.
Those porters have their own solution to altitude sickness and crises of willpower, one that would garner you a visit from a SWAT team in some countries but earns a nod of respect here: coca leaves. Roll them into a ball, wedge them into the side of your gums and chew.
The porters reckon it gives them a little kick along. No kidding.
But back to the trail. We're almost at the halfway point, "Dead Woman's Pass" - aptly named - 1½ days through the three-day journey to Machu Picchu.
The first day had been relatively easy, hiking through even terrain, but day two is the one that breaks most people, with its steep ascents at high altitude. Day three is gravy after that.
Of course, it didn't have to be this way. I could have taken the train. There's a track that runs all the way from Cuzco, the nearest large town, to Aguas Calientes right at the base of Machu Picchu. Plenty of people choose to take this easier option, arriving at one of the wonders of the world smelling fresh and clean.
Those who've hiked are easy to spot at the Incan city, with their dirty clothes and looks of smug content. There's the feeling you've earned it, that the ruins look even better when you've put in the hard yards to get there the traditional way.
But I didn't know any of this on that second day as I plodded, one foot in front of the other, towards that pass, grumbling to myself that this had better be worth it. I also didn't know that once I'd reached that pass there'd be an equally steep descent to the campsite, one which a personal trainer would probably say "blasts your core" but which just made me want to roll over to the side of the trail and quietly pass out.
The next day there'd be another full hike, plus a 3.30am wake-up call on day four to make it to Machu Picchu for dawn.
So, was it all worth it, getting to the end? Turns out that's a moot point. Because when I look back at the journey, I don't think about the majesty of those ancient ruins or the fulfilment of having made it to the finish line. In fact, I don't think about Machu Picchu at all.
I think about a soaring mountain pass and a good mate who'd sworn to leave no man behind. And that was worth it.
Have you done the Inca Trail or another travel experience that nearly broke you? Post a comment below and tell us about it.
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