When I was in high school I competed in speech and debate. I preferred expository speaking, but our coach insisted we try different events. In extemporaneous speaking you get a topic and then speak on it for about 5 minutes or so with only a minute or less to prepare. Depending on the topic, a sensible and non-rambling delivery can be tough to achieve.
Sometimes, I feel like the first draft of a children's story is like that. An idea pops into your head, you process the various tacks the story can take, and then you deliver your ideas on a blank page. If it rambles too much, you want to throw out the whole idea. Fortunately, writing gives you plenty of "do overs" (i.e. revisions) to harness your creativity and hone a great story. The trick is remembering you have that capability. The first draft is never the last (at least for 99.999% of writers).
And let me know how the elf and dragon work out the cupcake sharing...