Whatever you want it to be useful for. I use it to learn how to be more mindful, and especially right now, calm myself one hour before I go to sleep.
I feel that you need to introspect yourself if you really need the answer. I am, partially by choice, partially by passion, a minimalist. The essential is what I aspire to own, and that only. Nothing more, nothing much. Now it'sup to everyone to define what's essential. Usually most people know what's essential, they just ignore it to cover their flaws and their consumerism needs' product.