You must return to the fairy cave while children sleep. Fairies only exist if children believe in Fairyland. If you return after they wake from their dreams, you could remain frozen between two worlds for all eternity.
Dreams
If a fairy makes a wish to leave the fairy cave, she must return to the cave every year and always on her birthday to live as a tiny fairy on that day. If she fails to obey the Fairy Queen’s Rules, she’ll turn to fairy dust, forever.
4563