In A Farewell to Arms, what are some existential quotations or scenes?

In A Farewell to Arms, scenes that
explore individualism and/or an exploration of identity are good places to examine the
role that existentialism plays in the novel.  In short, existentialism revolves around
the idea that each individual must create his/her own self and that there is no
"essence" to what makes up a person.  At the beginning of the novel, the protagonist Lt.
Henry is left unnamed, which is an implicit reference to the existentialist idea that
Lt. Henry must "create" himself.  Before Lt. Henry meets Catherine Barkley, he has
little sense of individual purpose.  However, as their relationship progresses, Lt.
Henry builds his life around Catherine.  When the priest visits Lt. Henry in the
hospital, Lt. Henry, although sympathetic to the priest's ideas about God, cannot bring
himself to say that he believes in God, but he does believe in the relationship that he
has with Catherine.  Thus, he "creates" himself around the love that the two
share.