I think it's about truth. Emotional truth and artistic truth. Sometimes a storyteller has to do stuff he/she doesn't want to do because not to do it would be to sin against truth.

My Artax moment is in Kipling's Jungle Book- where Akela the lone wolf dies in the fight against the Red Dog. It's unbearably sad (or it was when I was nine or ten) but it's also true.

Another Artax moment is when Christopher Robin goes away to school at the end of the Pooh stories. It amounts to killing all the characters off. So many classic children's stories end with a dying fall- and so they should because childhood is a transitory state.