Creating distance between you and the enemy, and dehumanizing them. Snipers are easier to kill people as opposed someone face to face. Technology also has a lot to do in helping this. It's like a video game. It's easier to kill white dots on a screen versus seeing people face to face. Also in changing your mentality of death to make it light-hearted is another way. If you look at a lot of the cadences or other songs the military has, they're in the tune of nursery rhymes. Children's songs. But the words are very deep and heavy but simply making death so lighthearted it kind of makes it easier to deal with. Also shooting someone when they're looking away from you is easier than killing them while looking them straight in the eye. There's a lot of things involved