He was representing YouthCare Canberra, part of St John's Care Reid, and he did so with such force that one woman was so moved afterwards that she simply hugged him in gratitude.

"You've got to give these kids a piece of your heart because no one else is," is how he explained his job to the audience.

It's difficult to know where to begin with Bryers' story. He's been a homeless teenager, a soldier in Afghanistan, a gridiron player for Australia, a youth worker on call 24/7.

Most importantly, he's also a loving partner and father to two daughters. That role, in recent weeks, has become particularly emotional as his youngest daughter – just one year old – endured an eight-hour operation to remove a brain tumour.

"Leaving her on that table and walking out not knowing if you're going to see her again, I just burst into tears," he says. "I was a mess until she opened her eyes."

With partner Megan, they are rallying around Kalea and her older sister, Layla, who, at five, is also rocked by her sister's illness.

"We've had so much support. YouthCare is like a family. The directors, the board, are calling you: 'What can we do to help?' Working here, it becomes your life."

All this and Bryers is only 27.

He's also received several awards, including the outstanding youth worker of the year for the ACT, but he can't even bring himself to say that aloud, and only points to the trophy.

"I don't say it, because I don't believe it," he says. "My thing is, as soon as I believe that is true, I stop growing.

"It's a such a privilege to have people who are in a crisis ring you to help them. I think it comes with a lot of trust and a lot of responsibility."

Bryers will also be named on Wednesday as one of eight Canberrans to receive a prestigious Churchill Fellowship to travel the world to explore their chosen interest. He'll use his fellowship to visit the United States and Rio De Janeiro next year to see the "cure violence" program in action.

The non-government organisation that runs the program treats violence as a contagious health issue, treating it as an epidemic that must be contained and treated.

Bryers is YouthCare Canberra's first full-time outreach worker. The mix of interests that make up the man are evident in his small office on the historic grounds of St John's: his No.52 Australian gridiron jersey framed and on the wall next to quotes from Nelson Mandela, the Dalai Lama and Gandhi. "Be the change," the Gandhi quote says.

After hitting rock bottom, Bryers, little by little, challenge by challenge, worked to change his life.

He was born on the Gold Coast to a single mother. His father was never in the picture. "To illustrate my relationship with my father, I talked to him just before I went to Afghanistan to get a birth certificate and he said: 'I told your mother she should have had an abortion' and left it at that," he says.

When he was five, his mother returned to her native New Zealand but they had to flee back to Australia when her boyfriend tried to kill them.

He was an angry teenager. Angry that he was the poor kid. Angry at his mother because his father wasn't there to be angry at. Angry because he didn't know who he was.

His relationship with his mother broke down and Bryers left home at 15. First he couch-surfed. Then he was on the street.

"I'd walk all night, stay awake all night, so you're aware of what's around you, and then I'd sleep all day on the beach," he says.

"Just do what I could to feed myself. I wasn't on Centrelink, I didn't even know about Centrelink. I'd do what I could to get some money to buy a packet of Aldi chips or something."

A woman in her mid-20s, an acquaintance of his mother's, agreed to take him in, and that was the first good thing to happen. He now calls the woman his sister.

His goal then was to join the army. And for a heartbreaking reason. "I just wanted to die so someone would care and come to my funeral," he says.

He eventually took a less nihilistic view and saw the army as a way to save money to go to university. Bryers met his partner, Megan, and she helped him apply for the army when he was 19, training at Kapooka and Puckapunyal. He was eventually stationed at Townsville with 3rd/4th Cavalry Regiment, an armoured regiment, driving Bushmaster vehicles.

His first daughter was born in January 2011. He was deployed to Afghanistan five months later, stationed in the Tangi Valley, sitting in the desert for weeks but also getting shot at. "Got a few contacts – when you're in the army, that's what you join for," he says.

What's "still raw" is sitting on a plane back to Australia in November 2011, unable to continue service when he suffered "migraines on steroids" four times a day. He still agonises over whether he could have done more to stay in Afghanistan.

"I think the most addictive thing was that people were so proud of you and there's so much responsibility, and it's hard to come back and get that again, which I think is why I struggled," he says.

He was diagnosed with post-traumatic stress disorder and medically discharged from the army in October 2013. His self-esteem was "shot". "It was like: 'What do I do now?'"

His next step was quite remarkable. He started listening to motivational speakers on YouTube and decided to set a goal. "I'd never played gridiron but I'd watched it, so I set myself a goal to make the Australian gridiron team in 18 months," he says, planning to use YouTube again to learn how to play.

In the meantime, he and Megan moved to Canberra. He made the Australian gridiron team within 17 months, playing in the World Cup in the United States in 2015.

His new goal? Mount Everest before 2035. "I'm starting to do rock climbing and do some hill climbs locally to start the training towards it," he says.

Becoming a youth worker was another goal achieved. He understands the young people. He doesn't judge them. He doesn't order them around. He supports them and believes in them.

He helps them with the basics: how to talk to someone, how to ask about a job, how to deal with conflict.

He helps teenagers on ice and who are in and out of jail. He deals with the problem of how to house a homeless 14-year-old when there are only 24 emergency accommodation beds for young people in the ACT. He is on call 24/7.

"My biggest thing is asking kids what their dream job is. If you've got a dream job, you're planning to be around that long and it gives them something to hold on to," he says.

"It's a tether to society and hopefully we can build on that and connect them with services. As long as I know I haven't held back and given all I can, it allows you to have some sleep that night. And then you start again the next day."

Looking back on his own experiences, Zack believes his PTSD diagnosis was critical. It helped him take stock of his life. He knew he couldn't change anything; the fact that he'd survived and thrived was something he could find pride in.

He says he looked at how his father treated him and he does the opposite with his daughters. "They're my best friends," he says. He and his mother are now reconciled.

He feels positive about the future, not least because he is helping others. "I'm doing my dream job."