What does Kropp mean when he says of himself and his classmates, "The war has ruined us for everything"?in All Quiet on the Western Front

This quote points to the themes of
destruction and a lost
generation.  In chapter 5, Muller questions his comrades about their
plans for "after" the war.  Though this is a seemingly innocent (and somewhat
commonplace) conversation starter, it is actually received with mixed emotions.
 Unfortunately, because of the death and destruction they've not only witnessed, but
experienced, none of these boys will ever be the same again.  Though they talk of things
like women and drinking, the truth is, most of them cannot imagine life after the
war.

When he says, "The war has ruined us for everything,"
Kropp is talking about the comparison of life before the war to life after.  Before the
war, these boys were students who may have had short or even long term goals that likely
included typical things like careers and families.  The sheer trauma of what they've
experienced as a result of fighting on the front lines however, has put many of the
"childhood" goals and dreams in perspective.  In the face of that amount of death and
destruction, in the face of raw fear for their lives on a semi-regular basis, it is no
wonder none can imagine a regular life again.

This quote,
though spoken by a fictional character, embodies the simple but profound emotions that
such serious stress and trauma cause.  Kropp sums up the whole of the war in one word:
ruin.