Years ago, he had a member of his squad die in a Humvee crash when they were on assignment in Pakistan. He was in the car- he lived and his friend died. That was the start of the PTSD and could very well be tied to his need for perfectionism.
I think the other reason is because he works for a military company and has very specific short assignments when he goes overseas, usually just one to two weeks. He has an objective, he goes over, does what he must then flies home. From what he explained to me, each member of his team has a very specific job and they must trust each other to do it. If one of them fails, they can get hurt, or shot, or captured, or die or not accomplish what they need to- all bad things. When he asks me to do something, I believe he applies those same standards to me. Failure to him isn't an option, and when I fail (even if I genuinely try) no excuse matters. Like Yoda says " there is no try, only do" or something, lol.