In Slaughterhouse-Five, Kurt Vonnegut uses repetition and verbal irony (understatement and litote) to reveal that Billy Pilgrim has experienced many deaths and that death is inevitable.
Repetition: Vonnegut repeats "So it goes" near the ends of episodes and chapters to underscore that "death marches on."
Verbal Irony (understatement): Vonnegut says, "So it goes." Not only does time go on, but so does death. Also, Vonnegut says that Billy Pilgrim ‘‘has seen his own death many times." To say that a soldier of World War II and a survivor of the Dresden massacre has seen death many times shows that, in fact, he has seen death so much that he has become desensitized to it.
Litote: "So it goes" is a phrase that avoids saying what it really means: "it" equals "death." This is a kind of euphemism in which the author repeats it so much that he avoids making his narration sound so depressing.