In Relation to Slaughterhouse Five

I had a difficult time grasping the relationships in Slaughterhouse Five, beyond the fact that very few relationships seemed to develop, those that occurred remained vague. I suppose though that was the first indication that the relationships in the book were unhealthy. Billy remained apathetic towards most characters-- particularly emphasized by stating "So it goes." after every single death. However, I saw it as an indication that to form a relationship capable of helping or hurting someone, one must have a stable relationship with oneself. Billy remains damaged after the war, this manifests as his time traveling ways and dreamt up encounters, which prevents him from forming external relationships and even being a unified entity.
After reading the anti-war narrative, I was amazed at how Vonnegut depicted the effects of the traumas of war and how abstractly we could understand a distant and removed protagonist. Billy, to me, was harming his relationship with himself, even though he was coping with it the only way he possibly could. Although the relationships in the novel between characters seemed relatively neutral, maybe slightly damaging since there was apathy and removal on Billy's end, it was Billy in relation to himself that carried a more poignant message. Can one even have a strong relationship with another when you are in dissonance with yourself?