"So it goes"--how does it go?

As I immersed myself into chapter two I continued to notice a very repetitive use of the phrase: "So it goes." I noticed it a few times in the first chapter but it became a more prevalent motif in chapter two. It even appeared twice on one page where Vonnegut says: "Everybody was killed but Billy. So it goes. While Billy was recuperating in a hospital in Vermont, his wife died accidentally of carbon-monoxide poisoning. So it goes" (25). Some one who had read this novel before told me to watch for the phrase and upon pondering its meaning I have concluded it plays a role to show a negative feeling that he simply explains by saying 'So it goes.' He later explained this by saying that Billy picked it up from the Tralfamadorians and described that they said this phrase every time they saw a dead corpse. Thus i see it as Vonnegut's own unique way of showing that someone died without directly referencing it as thus far every time he mentions death it reappears.