Obeying the Rules of Grammar

There's one thing to remember about the rules of grammar: They are not rigid; they change as our perceptions of our language change. What satisfied our eighth-grade teacher certainly won't satisfy an editor, but then our eighth-grade teacher wasn't trying to be an editor. The rules, however, were there to be learned, and once we learned them, we could believe they applied only when they made our work better.

William Noble, Noble's Book of Writing Blunders, 2006