Born in Dapto and now living in Thirroul, Bryant had served in the Australian Defence Force as a dog handler for more than seven years.

After a short stint in civilian life he signed up with a security contractor and spent a decade in Afghanistan as a dog handler, helping armed forces to sniff out explosives, search vehicles and check roads for bombs and mines.

He would spend that decade going back and forth between Afghanistan and home, from facing firefights "every second or third day" to spending time with his then wife and children.

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After that decade, he "knew there was something wrong" - he was suffering from Post Traumatic Stress Disorder (PTSD).

And he realised that unlike the situation with soldiers, what a civilian contractor has to deal with was very different.

A 2013 report by the Rand Corporation in the US found that contractors were twice as likely to suffer PTSD than uniformed military veterans, yet they did not have access to the same levels of healthcare and support.

"Australian and US soldiers go over there for six to eight months deployment - I stayed there for 10 years," Bryant says.

"This is the thing with the contractors, there's no limit. You can keep going back as much as you want.

"And there's not much help there. With the US, they can fall back on their military and say there's something, I need some help'. They get a debrief on their way back out of the country, they get to talk to psychologists or psychiatrists to get to understand what they've seen.

"But with us, I was inside Taliban provinces fighting and three days later I'd be back at home with my kids."

While he says it was good to be back home, it still felt like he was in that Afghan war zone.

"It takes you a good two or three weeks to decompress and come back down from that environment to being back home," he says.

"What happened to me doing it for such a long period of time is my adrenaline got locked on, that's the best way to describe it.

"Like a car, you might be running at 2500-3000 revs a minute in your body. For me, normal could be 5-6000, so it doesn't take me much to redline, for my adrenaline to go up.

"What happened to me was that got locked on because I was exposed to it for such a long period of time, when I got home I'd still be redlining. I could be in a shopping centre, or doing something with my kids, and trying to understand why my body's still reacting the same way as it would be if I was doing something that really needed that fight or flight instinct."

He was diagnosed with PTSD in 2016 and that was when he'd decided he'd had enough and stopped going to Afghanistan.

"From there I decided I wasn't going to travel back and forwards any more," he says. "I resigned and stayed in the Illawarra."

He now lives in Thirroul and has had a career change - he's now a coalminer.

Together with author Tony Park (who also served in Afghanistan) Bryant wrote a book about his experiences - War Dogs - which was published in 2010.

That book dealt with the first four or five years of his service and an updated edition has just been published to take in his later years in Afghanistan and his time dealing with PTSD.

The idea behind the updated version was to shine a light on PTSD, both for himself and for others in the frontline - whether it be soldiers in a war zone or those in the emergency services back home.

"I don't suffer from nightmares or anything like that, though I know other soldiers or police officers who have. Mine is purely my adrenaline, it's locked on - hyper-vigilance is probably a better word for it."

Bryant says he tried medication to treat his PTSD but found it made him drowsy and he couldn't adjust to it. He says that hyper-vigilance is always there and he just had to find a way to manage it. For him, that meant lifestyle changes rather than a medication regime.

"I've just got to make sure that I'm still eating clean and healthy, I'm still going to the gym, I'm still doing a lot of cardio," he says.

"It's trying to stay healthy and having a balanced lifestyle, making sure I'm getting out with my friends and socialising with my partner and my kids and doing everything as right as I possibly can."

War Dogs is published by Pan Macmillan.