A friend and writing peer, Andy Cochran, shared with me this wonderful little piece by Stephen Fry on the joy of language (and the unnecessary focus on its "proper use"). It's a great reminder of how to think about context and meaning when we write, especially for children and young adults. Plus it gives writers license to be playful. Don't worry about "mistakes" in an initial draft. Cleaning it up can be fun, too, but just get out what you mean to say the first time around. Revise later.
And by George, it's okay to break some rulz every now and then--even in a revised draft!