"My thighs cramping up on the very first day ... the mental trauma ... physical adversity ... I felt a great deal of fear wondering how I would make it through the next month," says Akshay Nanavati.
The 30-year-old American businessman and former Marine is describing his 28-day run across Greenland in 2012, dragging a 190-pound sled.
"Waking up, swallowing down the most disgusting freeze-dried food, packing up our tents and skiing for up to 12 hours a day in temperatures so cold that on some days my entire beard would be covered in ice.
"This was my life for one month, except for the five days we were stuck in storms so powerful, the inside of our tent sounded like a washing machine."
"On some days my entire beard would be covered in ice," Nanavati says of his Greenland trip.
courtesy Akshay Nanavati
Nanavati finally completed the journey 20 pounds lighter in bodyweight, with mild frostbite on his fingertips, a swollen ankle and a sunburned nose.
And he's going to do it all again, about 190 times.
His mission is to run across every country in the world in the next 20-25 years.
There is no globally accepted definition for the number of countries in the world. The United Nations puts the figure at 193 and the U.S. State Department puts it at 195.
But that's a lot of running, whichever authority you listen to.
It's the first time this specific feat has been attempted, though other similar attempts have been recorded, and this former Marine is doing it in reaction to a Post-Traumatic Stress Disorder (PTSD) diagnosis he received after returning from a seven-month deployment in Iraq.
"When I returned home from Iraq, the VA (Department of Veterans Affairs) diagnosed me with PTSD," Nanavati tells CNN.
"I see now that it is not PTSD but post traumatic growth that has led to my decision to run across the world, because I choose to do something that inspires me to wake up every morning in order to make my life and the world better."
Robert "the runningman" Garside trekked across 30 countries in five years during the late 1990s.
(Editor's note: An earlier version of this story included information about Garside's run that has since been removed.)
Starting with four crossings covering 125 miles (201 kilometers), around the Caribbean islands -- Barbados, Grenada, Saint Kitts and Nevis and Antigua and Barbuda -- in June 2014, Nanavati aims to complete 20 countries by May 2015.
The runner's troubled history
"I began running at the age of 18 after recovering from a life of drugs that killed two of my friends," he says. "Running and physical fitness became my way out of that life and into the Marines.
"It replaced the high I got from drugs."
The adrenaline junkie then discovered skydiving, mountain biking, scuba diving, rock climbing, ice climbing; "anything that forced me to face my fears," he says on his website.
Then came the Marines, Operation Iraqi Freedom and the PTSD diagnosis.
If the runs themselves don't sound tough enough, Nanavati also plans to do it all while still running his current business, Existing2Living, which aims to help people achieve their potential.
That business will help with the funding of the trips, and he has some small sponsorships too, from running shoe manufacturers.
The most challenging trip will be one crossing Israel and Jordan, a 550-mile (885-kilometer) run planned for December 2014.
Nanavati's mission to run across every country in the world will take about 20-25 years, he says.
courtesy Akshay Nanavati
"Running allows me to experience the spectrum of the human condition: ultimate bliss, extreme suffering, complete stillness where there is no past and future and everything in between.
"In one run, I get to experience an entire human life."
His most hotly anticipated run will be across Rwanda, currently planned for August 2014.
"I wrote my history thesis about the genocide and am very fascinated by the resilience of humanity displayed by the people in [Rwanda]," says Nanavati.
"Not only will that trip involve the run across Rwanda, it will involve working with genocide survivors as well -- the overall mission of this project is about connecting with humanity."
Pain, fear and extra shoes
His mission will depend on meticulous planning and a willingness to embrace fear, he says.
"Every time I look at my itinerary and realize how much work I have to do, not just in terms of training, but also in terms of logistical planning, it terrifies me," says Nanavati.
He replace shoes every 350 miles (560 kilometers), requiring at least two pairs on each run.
"I have to not only plan for my next few runs, but plan for the ones after that as well to ensure success.
"On a 50-kilometer (31-mile) run last weekend, I went through many moments where I asked myself, 'Do I really want to do this for the rest of my life?'"
"But as soon as I got back home, I found a 50-miler (80-kilometer run) that I want to run next because, despite the pain, there is nothing like that feeling of reward that comes with accomplishing something that pushed your mind, body and spirit to its limits."