Some writers think they need to use fancy words, pull out the thesaurus and find something obscure, but most editors don’t like that. Use normal words, just not the same ones every time. If you say “ran” every time you indicate quick ambulatory movement, you might try “jogged,” “loped,” or “trotted” a few times in the book. If everything is blue, you might make something in your book red, unless a blue universe is important to your story. Highlighting the places where you wear out a phrase can help you see just how often you use it, and learning this about yourself will help you be a better writer.