I think it is pretty much an individual reaction. Having been in the position of identifying targets in an active war situation, while being semi removed from the fighting, most of my co-workers and I did not seem to be overly bothered by it. I am still in touch with some of them, they seem to have returned to civilian life with few problems.
Some people just can't handle the pressure of the job and internalize what they are doing, thankfully that was not my problem.
Probably the worst part of the job is that you can't really talk about it to anyone that is not directly involved, which has a tendency to spill over in all aspects of your interaction with family and loved ones.
Beard