This is my all time favourite end-of-talk question.
A Year 5 boy put up his hand and asked: "Do you get headaches?" I was surprised because I do. I get terrible migraines. "Yes. How did you know?" I asked. "It's so crowded with ideas inside your head, your brain must be stretched really tight," he said.
Then his friend spoke up. "That's why she writes books. To empty out her head so it stops hurting."
And in a way they are both correct. There are lost of times when I feel if I don't write it down my head will explode.
[PS Word of warning - never type 'exploding head' into a Google images search late at night. What you see will keep you awake for hours. And it's not public domain so you can't use it anyway!]