Cleaning can be therapeutic in a number of ways. It's good exercise. You can actually burn around 240 calories vacuuming for an hour. And you don't need an expensive gym membership to do it.
It also gives you an opportunity to reacquaint yourself with all your great stuff. Remember how much you loved that black lacquered tray when you bought it? And isn't it nice to take a closer look at that crystal candy dish? How about the carved, wooden candlesticks your dad made for you? It's easy to take individual décor items for granted once your room gets too cluttered to notice them. Cleaning can help you recollect why you liked all that stuff in the first place. Oh, and it can also give you some good ideas about minor updates that can keep your home looking stylish.