When former Army infantryman Tyler Heath was deployed to Iraq, he battled militants and became inured to gruesome sights. Once returning home to Colorado, he had to recalibrate.
The intense combat, the feelings of anger and violence, and the constant threat of insurgents became his new "normal".
"When you see a big, shocking incident, it changes you. It's terrifying. You don't know what to think or say; your training just kicks in," said Heath, now 26. But the next incident of a suicide bombing or other catastrophe had a smaller and smaller effect.
Even methods of pursuing insurgents, jumping curbs in cars and pulling guns, are far removed from life in the United States, he said. "You come back and you don't really fit in. You're not really connected to people like you used to be."
It was six months to a year before Heath realized he had post-traumatic stress disorder.
"I couldn't sleep or relate to anybody. Going out and driving was a challenge. Everyday life was just a challenge," he said.
It was then he started exploring treatment, including therapy. Although the available treatment, including talking through what brought on the PTSD, helps many veterans, Heath said for him personally, going to college and gradually re-assimilating into society helped the most.
"I just tried to separate myself from [the past] and get back to normal life and live with it rather than having every decision I made be wrapped up in having PTSD," he said.
Heath said his family also played a big role in helping him.
"They were supportive and understanding and patient. They were there when I had breakdowns and was crying and when I couldn't sleep," he said. "I came from a stable home and not every veteran has that."
Heath, who now lives in Lakewood, Colo., and is an avid skier, said what he experienced in Iraq will always be in the back of his mind.
"I heard a lot of veterans say civilians just 'don't get it.' But they didn't fight those wars, so of course they don't and you wouldn't want them to get it," he said.
Heath said he hopes to correct a view some people have that those with PTSD are less capable. "PTSD makes you stronger because you've done things that are out of the normal realm of what humans do."
Now when he's asked to stay late at his job at a company that provides computer support to businesses, it seems like nothing after experiencing days-long patrols with no sleep, he said, laughing.
And the view that some in the military sill have that PTSD is a weakness needs to be corrected, said Heath. "They say you're not a good soldier because you developed this. But it's to be expected. If you go into combat and fight in a war, you're going to get this."
PTSD is estimated to impact 10 percent to 30 percent of service members, depending on their level of combat.
Heath also emphasized that veterans who have PTSD are not alone. Just knowing that when he thought he might have the symptoms, "made a huge difference," he said.
Tyler Heath is featured in a NewsHour report, expected to air Monday, on the University of Colorado's "Boots to Suits" mentoring program for veterans. View all of our international and military coverage and follow us on Twitter.