At the start of World War II, President Roosevelt wrote out his speech. And then he revised it.
http://www.archives.gov/education/lessons/day-of-infamy/index.html

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When you edit and revise, you should feel free to change whatever you need to in order to make your work better. Find the right words. Change the order of the sentences. Move paragraphs. Start from the beginning and try it again if you would like. Every bit of effort will make you a better writer and will improve your ability to communicate clearly and effectively, and your audience will better understand you and be affected by the message you are sharing.

Here are some materials and websites that might help you work on your editing and revising.

How to Write Clear, Concise, and Direct Sentences

Twelve Common Errors: A Student Self-Editing Guide

Proofreading