Basically the entire story is based around the changes in the characters, particularly the father.  His decision that he really needs to be more cheerful in order to be successful helps to highlight the real conundrum of the story which is really the chicken or the egg question.  Because the story centers on the egg itself, it is the changes of the characters and their actions around the egg that serve to bring out its meaning.  For example the fact that the father, in the midst of his rage, still cannot bring himself to destroy another egg brings up all kinds of ideas about an egg being full of life or at least a symbol of it.