There is a special kind of exhaustion the world's best endurance athletes embrace. Some call it masochistic; others may call it brave.
When fatigue sends legs and lungs to their limits, they are able to push through to a gear beyond their pain threshold. These athletes approach fatigue not with fear but as a challenge, an opportunity.
It is a quality that allows an ultramarathoner to endure what could be an unexpected rough segment of a 160km race, or a sailor to push ahead when she is in the middle of the ocean, racing through hurricane winds alone.
The drive to persevere is something some are born with, but it is also a muscle everyone can learn to flex. In a way, everyone has become an endurance athlete of sorts during this pandemic, running a race with no finish line.
Some of the world's best extreme athletes share what they do when they think they have reached the last straw. How do they not only endure but thrive in daily challenges?
One message they all have: You are stronger than you think you are and everyone is able to adapt in ways he or she did not think possible. But there are a few techniques to help you along.
1. Pace yourself
Training to become an elite endurance athlete means learning to embrace discomfort.
Instead of hiding from pain, athletes must learn to work with it. A lot of that comes down to pacing, says sports psychologist Carla Meijen.
Similarly, as you muscle through an ongoing pandemic, you must look for ways to make peace with unknowns and new, uncomfortable realities.
"When we think about the coronavirus, we are in it for the long run, so how do you pace yourself?" says Dr Meijen, a senior lecturer at St Mary's University in London.
She recommends thinking about your routines, practising positive self-talk and focusing on processes instead of outcomes. You do not know when the pandemic will end, but you can take control of your daily habits, she adds.
Conrad Anker knows something about that. The celebrated 57-year-old American mountaineer has, among other things, ascended the Meru Peak Shark's Fin route in India and thrice to Mount Everest's summit - once without supplemental oxygen - and survived a heart attack while climbing in the Himalayas.
He advises people to "always have a little in reserve". Deplete your resources early and you will be in trouble. Focusing on day-to-day activities will pay off in the long run. If you use all your mental energy in one day or week, you may find it more difficult to adapt when things do not return to normal as quickly as you hope.
"When you get to the summit and you use every single iota of energy and calories to get there, and you don't have the strength to get down, then you're setting yourself up for an accident or for something to go wrong," says Anker. "Don't play all your cards at once and keep a little something in reserve."
2. Create mini goals
Sports psychologists frequently recommend creating small milestones en route to a big goal.
"Setting goals that are controllable makes it easier to adapt," says Dr Meijen. "If you set goals that are controlled by other people, goals that aren't realistic or are tough or boring, those are much harder to adapt to."
American professional ultrarunner Coree Woltering is skilled at conquering mini goals. The long-distance runner has stood on the podium after races from 50km to 160km.
This summer, he set his sights on breaking the running record on the Ice Age Trail, some 1,845km across Wisconsin. He ran more than 80km a day, for three weeks, to accomplish the feat.
"I'm really good at breaking things down into small increments and setting microgoals," he says.
How micro? "I break things down to 10 seconds at a time," he says. "You just have to be present in what you are doing and you have to know that it may not be the most fun - or super painful - now, but that could change in 10 seconds down the road."
And it may not change quickly. Woltering has spent six-hour stretches counting to 10 over and over again.
"You just keep moving and keep counting," he says.
"And you have to have faith that it will change at some point."
3. Create structure
Dee Caffari, a British sailor and the first woman to sail solo nonstop around the world in both directions, says structure is imperative to fight loneliness and monotony.
On the sea, she would base her structure around a twice-daily weather report and all decisions would follow from there.
She is taking the same approach during the pandemic at home on the South Coast of England, replacing weather forecasts with outdoor activities.
She says: "In your day, you need structure. You need to get up in the morning knowing you're going to make something happen."
4. Focus on something new
When all else fails, look to something new: a new hobby, goal or experience.
During a particularly hard patch of a competition, some athletes say they focus on a different sense, one that perhaps is not at the forefront of their mind when the pain sets in.
A runner could note the smells around her and a climber could note the way his hair is blowing in the wind.
When athletes are injured, sports psychologists and coaches often encourage them to find a new activity to engage their mind and body.
The key is to adapt, adapt and then adapt again.
"We all want mental toughness - it's an important part of dealing with difficult things," says Dr Michael Gervais, a psychologist who specialises in high performance and hosts the Finding Mastery podcast.
"The current definition of mental toughness is the ability to pivot and to be nimble and flexible."
Caffari has shifted to spending a lot of time in her garden, something she did not have as much time for when she was travelling for much of the year.
"The neighbours are quite happy with that," she says with a laugh.
Anker has put his extra energy into calligraphy. "Yesterday, I transcribed quotes from John Lewis and I find that satisfying," he says.
When his favourite trails were closed because of lockdowns, Woltering decided to run every street of his home town in Ottawa, Illinois. It was about 320km.
"The next moment is always completely uncertain and it's always been that way," says Dr Gervais.
But adapting, adjusting expectations and discovering new goals or hobbies can allow you to continue to build the muscle that is mental toughness.
The bottom line? "Optimism is an antidote to anxiety," says Dr Gervais.