Write about what would happen to novel or fairytale characters if they existed in real life. Think about practical conventions that might surprise them. For example, Prince Charming (Sleeping Beauty) might balk at getting a job; Jo March (Little Women) isn’t an obvious candidate for make-up vlogger.
Write about your future. What will a typical day be like for your adult self? Will you still live near where you live now? Will you have the same friends? What will your family be like? What will you be doing?
Write about what you’re thinking about in this exact moment. It doesn’t have to make any sense.