It's a fact: people don't like change. Fear is a big part of it, then there's the fact that "when you've been doing something a particular way for some time, it must be a good way to do things. And the longer you've been doing it that way, the better it is" (source).
Warm Bodies tackles this head on. There's fear—the Living have isolated themselves in a stadium away from the dead. And then there's something that we humans have been doing since the beginning of time: dying. Warm Bodies decides that dying isn't the only way to do things, even though we've been doing it for a long time, and R and Julie try to change it. We wish them luck, but we're pretty sure death is the one thing that will never change.