I was reading Blackfive today (an excellent US milblog) and saw this post linked.
It’s a great piece written by a (AFAIK) non-Christian former soldier (Marine perhaps) about Post-Traumatic Stress Disorder. (emphasis mine)
What you need to know, first and last, is that so-called PTSD is not an illness. It is a normal condition for people who have been through what you have been through. The instinct to kill and war is native to humanity. It is very deeply rooted in me, as it is in you. We have rules and customs to restrain it, so that sometimes we may have peace. What you are experiencing is not an illness, but the awareness of what human nature is like deep down.