'each man would, in his own way, be sort of gone'

Before leaving on this mission, many of the men in Colbert's platoon had said good-bye to one another by shaking hands or even by hugging. The formal farewells seemed odd considering that everyone was going to be shoulder-to-shoulder in the cramped Humvees. The good-byes almost seemed an acknowledgment of the transformations that take place in combat. Friends who lolled around together during free time talking about bands, stupid Marine Corps rules and girlfriends' fine asses aren't really the same people anymore once they enter the battlefield.

[...]

This is not to say the terror goes away. It simply moves out from the twitching muscles and nerves in your body and takes up residence in your mind. If you feed it with morbid thoughts of all the terrible ways you could be maimed or die, it gets worse. It also gets worse if you think about pleasant things. Good memories or plans for the future just remind you how much you don't want to die or get hurt. It's best to shut down, to block everything out. But to reach that state, you have to almost give up being yourself. This is why, I believe, everyone said good-bye to each other yesterday before leaving on this mission. They would still be together, but they wouldn't really be seeing one another for a while, since each man would, in his own way, be sort of gone.

—Evan Wright, Generation Kill (2004)