It's an inner weakness all endurance athletes seem to share. That masochistic streak that makes you wonder how deep you could really go before the wheels fall off...
For cyclists the testbed for that is climbing, and of late one particular challenge - Everesting. The concept is simple: find a hill and ride up and down it repeatedly until you've climbed 8,848m, the height of Mount Everest.
To date 2,283 people have done it in 73 countries worldwide. That's around 21million metres of climbing.
There are pretty strict rules: you have to complete it in one go, not stagger it over a few days; you can't sleep; and crucially you have to submit your data via Strava or VeloViewer and prove you've actually done it.
Here in Cyprus only two people had completed the challenge - one on a quiet climb near Limassol; the other on the road between Skarinou and Lefkara back in 2015. I quite fancied becoming number three.
On average it takes around 20 hours to ride an Everest - the fastest time ever was a guy in Australia who managed it in eight hours and 46 minutes. I was realistic. I wasn't going to trouble that.
The first task - find a suitable hill. This is a tricky one. You want a climb with good elevation, but nothing stupidly steep. For me that meant something in the 7% range.
I train to the west of Limassol and cycle up and down the road from Kourion to Episkopi all the time. It's a 1.5km climb averaging about 6% but it only rises by 84m. It's my perfect climb. But when I banged the segment into Patrick McNeil's brilliant Everesting calculator it said I'd need to ride it 108 times....
The other option was the climb from Akrounta near Germasogeia up towards Dierona. On Strava this segment's called 'Sporting Club Testing' - it's used by a few local teams, and overseas cyclists (lots of them impressively built Russian women) to gauge their fitness.
This had lots of plusses. I knew it pretty well, plus it was one of the two climbs previously 'Everested' in Cyprus before. The stats were also more inviting:
Now I'm no mathematician (as you'll soon find out) but I bunged in the data and it seemed doable. The previous guy (hats off to you Mad Mike whoever you are) had done it in 17 ascents, and completed the job in under 15 hours. It was a bit of a schlep from home, but I have a work colleague living nearby and I knew I could depend on her for food and anything else if I needed help. We were on.
I did some research and it seemed a lot of Everesting attempts take place through the night. People on various forums suggested sunrise activates some part of your circadian rhythm and you get a second wind. My experience of falling asleep at the wheel while driving home from night shifts at Sky News seemed to suggest otherwise. Also Akrounta is pretty isolated. So I compromised - I'd start around 0500. Still dark, but not a true night ride.
So early one Sunday I headed for Akrounta. I established my 'base camp' at the foot of the climb and set off, waking every dog in the area it seemed. It was a bit spooky to be honest. There was a touch of American Werewolf in London about it.
I'd done my best to prepare. I was training pretty hard for a trip to the Alps so I was fit. I'd also stocked up with as much water, food and music as I could get, and I had a change of kit ready for later in the ride.
A friend had even given me a tube of caffeine-laced apple pie used by US Air Force pilots to stay awake on long missions - "It's rocket fuel man," he told me.
The key to all this of course is recording what you do. No data, no Hall of Fame. The Everesting people are quite gracious and will allow you to 'stitch' together data from Strava and your Garmin for instance. But the last thing you want is for some technical malfunction at 8,847m.
I run an Elemnt Bolt and I'd emailed Wahoo to see if it would still record while charging. The Elemnt, I was told, would record and charge at the same time so I bought a portable AA battery pack off eBay that would top it up on the go. Job done.
And so the ride began. Some brave (and much younger) riders try and monster these Everests. I wasn't going to be one of them. My plan was to try and stay in Zone 2 throughout, with each climb taking around 35 minutes, and each descent around 12. Basically, an up and down every 50 minutes or so.
The first half dozen were actually very pleasant. I did however make one depressing discovery early on. My wife had loaded my iPod with a load of motivational tunes. Not quite 'Eye of the Tiger, but that kind of stuff. Problem was she'd got them from an 'unofficial' source, and that meant the end of every song was cut short by 30 seconds. Imagine the Beatles 'Day In The Life' without the big ending. Kinda depressing.
After a while it became too much (that, and the Motown she’d somehow added) and just an hour into the ride I switched it off. This was to be a silent mission.
By mid-morning I seemed to be doing surprisingly well. I'd pushed through the 3,000m mark and several friends turned out to ride the odd climb with me. I was still pretty feeling fresh and my pacing seemed spot on. The signs were good.
Keeping tally of your ascents is pretty important so I devised a simple plan: As well as drinking and eating, I'd place one small stone on the back of my pick up every time I got back to base camp.
By early afternoon I had nine stones. But I was also now on my own. Just me and the mountain. It was also getting hot. Very hot. The Spring temperatures of the previous weeks had vanished and I could sense my body temperature was rising alarmingly even though I was guzzling loads of fluids.
At one point my Wahoo recorded 47C which at the time was pretty alarming. I've since discovered that the Elemnt is prone to exaggerating temperatures if it's plugged into an external power source.
On I ploughed. I'd read somewhere that 4,000 - 7,000m are the hardest psychologically and so it turned out. Even though your legs are turning your mind drifts off. I remember thinking long and hard about a KFC bargain bucket and debating the rights and wrongs of Brexit.
As I rode through the 6,000m mark though things got a bit weirder. Every time I approached a particular rock formation I could swear there was an astronaut standing there watching me. I could see a space helmet, gloves, the full Apollo Mission suit. As I got close it would slowly dissolve back into rock. I was clearly starting to flag.
Despite seeing things my segment times and power were still pretty consistent. However, the 11% ramp towards the top was taking more and more out of me and I was zig-zagging for the first time I could remember.
Mid-afternoon brought some culinary salvation. My colleague Tess arrived with food - roast chicken, potatoes and egg salad. I climbed into the boot of her hatchback and devoured it, trying to find any means possible to avoid the sun.
And here's another consideration of Everesting - how many breaks you take and how long for? The advice is make them short. They add up quickly and you lose both time and momentum. Mine added up to more than three hours in the end. Oh, and if you’re base camp’s near a public loo even better.
So with a boiled egg in my pocket giving the impression I'd developed an impressive hernia, I set off upwards again. In the boot of my truck the line of stones slowly grew: 11, 12, 13, 14. As sunset approached I was on 15, and had clocked up 6,800 or so metres.
The previous Everesting on this climb had included a steep 150m section at the bottom just as you leave Akrounta. I'd asked a few friends and the consensus was to avoid it and start a little further up.
It didn’t seem much at the time, but those few metres were now adding up, and rather than the 17 ascents I'd calculated (my dodgy maths) it was dawning on me that it was going to take around 22.
At the end of ascent 15 I sat down and thought it through. I was flagging but I wasn't broken. And I had enough food and water. I even had some dodgy Motown. My concern though was mental.
I'd already had a few close calls with cars and trucks - including a Porsche and Mini Cooper re-enacting Fast and Furious 7 close to my handlebars - and as night fell more and more vehicles started heading up and down the hill.
Would they expect to see a skinny, shagged out bloke on a bike (albeit with lights) as they drifted round a corner channeling their inner Vin Diesel? Probably not.
And descending in the dark, while totally knackered (and seeing imaginary astronauts) is never recommended.
So on ascent 16, after breaking through the 7,000m barrier, I called it quits. In military parlance I 'banged out'. Heat, hallucinations and self-preservation had won the day. It wasn't worth dying for.
I was gutted but also relieved; I'd been riding for 12 hours or so and fallen short by a mere 1,800m. That really wasn't too shabby.
As I unpacked my vehicle I came across a little gift from a good cycling friend - a small, sealed plastic bag, containing a tightly wrapped t-shirt marking my Everesting success. Inside he’d tucked a drawing of a cake and the words 'To Be Opened Upon Completion'.
I didn't have the heart to open it and it still sits in my garage, staring at me every time I go for a ride - reminding me that one day I'll have another go.
Everesting it seems is rather like childbirth (ladies, please bear with me) you soon compartmentalise the agony and pain, and for some crazy reason want to do it all again.