I'm a firm believer that we children's book writers have a lot in common with writers of Romance Novels. So much so that I belong to the local Maryland chapter and usually attend the Romance Writer's of America convention whenever it is held here in the Washington, DC area. Their workshops have so much information for mid-list writers of all genres.
I also follow the blogs of several Romance Writers' agents. (for the same reason)
For example, Rachelle Gardner has a guest post on her blog from one of her writers, Camille Eide, talking about the Editoral Letter and how writers react to it.
I've gone through all of the stages she mentions whenever I get one, myself.