There is an individual in the United States, retired Lieutenant Colonel David Grossman, who has written a book on killing and on combat, and his views are quite unconventional. Interestingly, among conventional armies he's treated in some quarters as quite an expert in the field, but among special forces and police forces his writings are really adhered to. He has written about techniques to separate the emotions of the moment from the memory.
I couldn't begin to get into the details of how he does it. Suffice it to say that he's in very big demand. I'm trying to get him to come to this symposium that I'm trying to organize on operational stress injuries, and he's not available until the middle of next year. So he does have some anecdotal credibility.