Write about the day after you reached a goal.
What do you want to achieve? What changes then?
Everyone gets the same subject. What differs is the follow-up: one question for children, two for teens, three for adults. Only the children's wording is simplified.
Find the sentence you are least sure about. What you actually meant is usually hiding there.
Skip it and start at the second. The opening writes itself once the rest exists.
Delete every line anyone could have written. What is left is yours.
Write the visible, not the felt, and the reader stands there with you.
Open with a question and the reader keeps going to find the answer.
One line against your own view makes the whole piece stronger.