Writing as a way of thinking
An idea can feel complete right up until the moment you try to write it down. The sentence that refuses to come out is usually pointing at the part you have not worked out yet.
Write for one reader
Picturing a single curious person keeps the explanation honest. It discourages both jargon and padding, since neither would survive a real conversation.
Short drafts, often
A few rough paragraphs written today are more useful than a perfect essay planned for later. Most of them can be thrown away, and that is fine.