Remarque's All Quiet on the Western Front is full of incidents which dramatically change characters' perspectives on all kinds of things.
When Paul goes home, he has several changes in persepective. He realizes that people do not understand (largely because of a successful government propaganda campaign) that this is an awful, gruesome war and they are not winning it. Though he suspected it before, Paul realizes there is nothing here for him after the war--if he comes home alive.
Throughout the novel, soldiers who arrive at the front lines are continually shocked and often traumatized by the experience. What was a tidy and glorified ideal is now a horrific and terrifying reality. Death is near and greedy.
Experiencing death in some way is always an occasion for a change in perspective; and plenty of young men, both strangers and friends, die in this novel. The events which trigger such a change do not always need to be terrible; what they must be is life-changing, and this is a novel of many such events.