Paul is surprised at Kemmerich's mother's grief because it is so overwhelming - so much so, in fact, that it is impossible for Paul to convey it properly:
I cannot write that down. This quaking, sobbing woman who shakes me and cries out on me: 'Why are you living then, when he is dead?' - who drowns me in tears... (chapter 7)
Paul feels sympathy for Kemmerich's mother but at the same time he is rather impatient with such a show of emotion. He has been through so much by this time, he has seen so many people die at the war front that he can no longer understand such an outpouring of grief over just one individual. He has had to learn to control such emotions himself. This does not mean that he suffers any less, however; although he does not show it outwardly, the agony he feels during the whole time while on leave is almost worse than anything he has to endure during battle. He struggles to re-capture his old life at home, but cannot; it is gone forever.