I tried to stop working for 3 months and basically had an existential crisis and mild depression before coming back to work. I don’t agree you have to create something “useful” by its true definition. Do work that makes you happy and satisfied and hopefully that work also contributes to the betterment of humanity. Art is a perfect example of something many might not consider “useful” but imo sounds like an amazing life as long as you can afford to do it. Another one may be retiring from grinding work and opening a restaurant where you create amazing meals and experiences that make people happy for years and years. I still think about the generational family owned restaurants in Italy. There is no one-size-fits-all answer here. But “retiring” and just floating around doing nothing with your life is sure fire way to become a very unhappy and unfulfilled person.