Don't go to war.

Article: Moral Injury:

...[N]ew ideas are vying for legitimacy, a whole new theory of war’s worst ravages. It’s called “moral injury,” and it comes from clinicians who spend their days speaking with soldiers who have been in battle. These veterans rarely mention fear. Instead they talk about loss or shame, guilt or regret. They had tried to be heroes, to protect the weak, save their buddies, take the hill. But then they mistakenly killed civilians, forced themselves to drive past wounded children, sometimes missed their moment of truth. Even after the Battle of Fallujah, in 2004, where William Nash served as a combat psychiatrist, fear wasn’t a factor. “Survivor’s guilt, moral injury, feeling betrayed by leaders,” says Nash, the lead author of the current Navy and Marine doctrine on stress control, “That’s what I saw every day.”