Making sure that the purpose of your writing is clear to your audience, that your main ideas are supported with details and examples, and that your organization is logical are the goals of drafting, revising and editing. When writing something, the author necessarily should reread what he had written to make sure his main idea would be understood correctly, that he or she uses the words which describe the situation or event in the best way. That`s why all experienced authors use such techniques as drafting, revising and editing.
the primary purpose of that is to show everything have both a good side and a bad side also to show that not everything is what you think. It also explains some of the good old days stuff like in the book it first describe as feeling nice and warmish then starting to hurt