Dennis Maddock never realised the damage that 19 years in the military was wreaking inside his mind until it was too late.
As an officer, he took part in some of the fiercest fighting in East Timor. Each traumatic incident built up inside him until the cumulative distress broke his psyche and he went down with severe depression.
“I’ve been shot at. I’ve run into fires where we don’t know what’s going to happen when we’re inside the fire," he said.
But the mental pain was tougher than the physical. "It’s the hardest thing I’ve ever faced."
He had no way of knowing how the repeated incidents of violence were affecting him. He didn't have the right tools.
But now he does and he is teaching others a new way of monitoring mental health.
It's called the "Road to Mental Readiness" - R2MR - and it's a method used in Canada by the military and fire, ambulance and police staff.
It's being imported by Lifeline Canberra, which helps people in danger of taking their own lives. "It's a totally new concept for Australia," Lifeline Canberra chief executive Carrie Leeson said.
At the core is a way of monitoring small changes in behaviour that are warning signs of bigger, on-coming mental problems.
People who work in potentially traumatic occupations are taught to think of their mental state in colours from green (healthy) through yellow and orange to red (very ill).
Each stage lists a whole set of symptoms like irritability, alcohol over-use or sleeplessness right up to suicidal thoughts in the worst, red zone. All employees in vulnerable professions are trained to spot their own and their colleagues' symptoms.
Mr Maddock said that if the system had been there as his mental condition deteriorated, he would have been able to spot the early warning signs.
"It would have prevented me going down," he said. "I would have been able to understand what was happening."
The method has already been used in Canada and assessed rigorously by academics who have pronounced it effective.
In the city of Mississauga on Lake Ontario, for example, fire-fighters use it.
Fire Chief Tim Beckett said one of the benefits was that it reduced the stigma attached to mental illness, particularly among men in macho jobs where toughness is at a premium.
He said that under the scheme, problems became more easily shared. A colleague might say, "Are you OK mate? Want to talk?"
When people come back from a horrific incident, they discuss their own feelings. Managers are trained to spot bad signs.
Apart from the way of identifying mental issues that are building up, another part of the R2MR program involves teaching people how to breathe deeply and lower tension in frightening situations, either on the battlefield or in civilian emergencies like road crashes or fires. It's called "tactical breathing".
Police might use these techniques to lower stress before bursting into a house with hostages, for example.
Soldiers and emergency workers also learn techniques to boost their confidence to counter the self-doubt that trauma and fear induces, sometimes during an operation.
First responders sometimes have feelings of guilt if they have not been able to save a life, even where the situation was so bad that no life could have been saved by even the best of people. The program helps the responders talk through that situation, sometimes with each other and sometimes just internally, inside their own minds.
In Canada, one of the fire fighters in Mississauga endorsed the system.
Allan Mills barely escaped with his life in two big explosions, once where a warehouse caught fire and a wall collapsed on him and two comrades, and the other where an Air France jet crashed at Toronto airport in 2005.
He told The Canberra Times that in the first explosion, "I was thrown 20 feet through the air and was buried under a collapsed concrete block wall. I was uncovered from the rubble and dragged four hundred feet through concrete debris by my crew mate to escape the inferno."
And in the second traumatic event when the Airbus A340 crashed, Mr Mills said, "We carried the last passenger suffering from a broken femur to safety just before the aircraft fuel tanks exploded in flames. My crew mate and I were beside the tail section and had to run to escape the fire and debris raining down on us."
He has suffered mentally and physically ever since. He said one of the benefits of the program coming from Canada to Australia is that it brings mental stress into the open.
"When I came into the job, older firefighters were struggling. You had to be the tough guy. That was me. I was the officer of the crew and after so many years of it, it was wearing me down," he said.
"If I'd had this program in the early days, I could have recognised my own drop in resilience."
It has already been endorsed by an Australian hero who has been to Canada and seen the program in operation.
In 1996, police officer Allan Sparkes rescued an 11-year-old boy from a flooded storm water drain despite being repeatedly swept away by the torrent. He's been awarded Australia's highest decoration for bravery, the Cross of Valour.
But the trauma damaged him mentally: "There was just this sense of hopelessness with my situation that I believed I could never ever recover from."
He wished the Road to Mental Readiness program had been there for him. It helps by "giving people hope that they can get back to health again".