When you are writing, consider 15 minutes a long time
Sometimes, an experienced writer elf will write a title or a sentence or a paragraph and that is all. Then she (or he) will come back to the story later—later that day, or the next day—to write a bit more. It is very rare to write a story all at once. Very few elves have ever done such a thing.
Therefore, whenever the circumstances allow, elves work on stories over many days, a little at a time. Our expectation is that stories take time.
You might feel that the story characters are impatient when you put down your pencil to take a break! This is good! This means that your characters are pleased with what you are making.
You might think that you will forget a story if it is written over so many days. Quite the opposite often takes place: we continue to ponder and play with the story even while doing other things. (Of course, we can jot down any sudden ideas in a journal; this is so quick and easy.)