"We passed him on the way up." Alyssa Azar has climbed over bodies on Mt Everest. Twice.

While Alyssa Azar was climbing Mt Everest, there were occasions where she couldn’t think more than 10 steps ahead.

Reaching the summit of the world’s highest peak is undoubtedly a huge physical task, requiring years of training and preparation. And then, when the training is over, the trek up Mount Everest still takes months.

But beyond the strength, fitness and grit required to reach the top of the world, there is another challenge to be mindful of: The mental one.

The ugly business of climbing Mount Everest. Post continues after podcast.

“Mentally, it’s a whole mix of things,” the 22-year-old told Mamamia. “Sometimes you’re looking at the big picture, focusing on ‘I’m on Everest, this is huge’. And then other times, you’re just focusing on the day-to-day.”

“That was a piece of advice that I certainly had from mentors of mine before I went: Focus on each task, each day, really be in the moment and it will all come together. I found that was really helpful during the toughest times on the mountain.

“If you look too far ahead, you mentally psych yourself out, it feels really overwhelming. If you just focus on, when it got its hardest, the next 10 steps. Just take 10 steps and do it again and again and again and before you know it you will get somewhere.

"You certainly have moments when you just hit the wall mentally and you think 'I don't know if I can get up' to the next camp and you push through and you do."

Alyssa has reached the summit of Mt Everest twice.

In 2016, she became the youngest Australian to reach the summit at 19 years old. In 2018 she climbed the mountain from the north side, in Tibet, and became the youngest woman to summit Everest from both the north and south sides.

One of the most common side effects of trekking Everest is altitude sickness, particularly as climbers reach above 8000 metres - known as Everest's 'death zone'.

Alyssa didn't suffer altitude sickness, but that didn't mean she skipped the symptoms of being so high above sea level.

Base camp alone is 5300 metres in elevation, which means there is 50 per cent of the oxygen at sea level. Anyone there will already be feeling the effects of altitude, and they can increase as climbers trek higher up the mountain.

"There's a very thin line up there between being okay and getting sick," Alyssa explained. "So definitely headaches, they're pretty normal. You get headaches particularly when you get up to those high altitudes and before you really adapt it is a shock to the system."

"You're [also] really fatigued, so even the most basic daily activities of getting your boots on and walking around camp feel really exhausting at first."

Vital human tasks like eating and sleeping become a struggle at altitude, making the already dangerous climb even more treacherous.

"You've still got to be able to climb and perform despite the fact you're not really eating or sleeping well," Alyssa said. "It definitely is a mental game. Being able to manage the daily discomforts of altitude is a big part of climbing on Everest."

Though a bucket list item for so many of us, the reality of climbing Mt Everest is not to be taken lightly.

There have been 11 deaths in two months as a record number of climbers rush to conquer Everest in 2019, with this year’s weather providing only a small number of days with conditions safe enough to summit.

This resulted in a 'traffic jam' at the top of the peak this month, which may have contributed to the deaths of climbers who spent longer than advised at the top of the world.

There has been at least one death every year since 1977.

Therefore, the prospect of not returning from the mountain must always be on an Everest climber's mind.

"I was prepared for that outcome and so was my family, we discussed that at length," Alyssa said of possibly dying on the mountain.

"I messaged before I left base camp for my final push and said 'I'll obviously make the right decisions and do what I can,' but this is a really unpredictable environment and you can be really fit and strong and still not know how your body will react to the altitude on any given day.

"It doesn't take a lot for you to get sick, so I was conscious of that. Especially when you are up at camp four [the final camp before the summit] and you're going over that 8000m mark, you are conscious of the fact that your life really is in your own hands.

"There's not a lot of assistance, there's not a lot of help, you have to be able to get back down much lower in order to get any help.

"It was always in the back of my mind, no matter how happy I was to reach the summit. You just know 'Alright, now I have to be really focused on the way back down.'"

And if one forgets the danger of the hike, they are never too far from a harsh reminder.

Everest is the world’s largest open-air graveyard, littered with the bodies of those who have died while climbing it. Many bodies – most of which are in the death zone – have become markers for others attempting the climb.

Weather conditions, terrain and low oxygen levels make retrieving bodies high on Everest near-impossible – and even if you’re willing to try, an expedition to recover remains from the death zone can cost more than AU$110,000.

Alyssa said she saw bodies in the death zone during her ascents.

A day before her summit push last year, when climbing from the Tibetan side of the mountain, Alyssa heard about a fellow climber's death.

"We heard that a Russian climber had died due to altitude sickness near the summit and we passed him on the way up.

"I think it brings it home. These are the people you were at base camp with, so you sort of know [them] within the community, and you think 'Why them and not me?'. It certainly makes you realise it very easily could've been me."

Three years on from her first summit, and a year after her second, Alyssa has had plenty of time to reflect on her accomplishments.

She described the feeling of conquering Everest as "surreal".

"At first, you're just elated. You're on cloud nine for a few weeks," she said.

"There's certainly challenges with it as well... It's a pretty intense experience in a lot of ways, good and bad, so it takes a little bit of time.

"You still have to remind yourself all the time like 'Oh that's right, I can't believe I reached the summit'. I wasn't sure that I could. I always believed in it but you never know until you prove it to yourself."