The last time I moved, I tried to whittle my belongings down to around 100 things. I don't think I ultimately succeeded, but certainly reducing my belongings down to the essentials made a huge difference in my happiness and decreased my stress levels. Every belonging demands some form of attention, such as storage and maintenance, and each item consumes mental energy, such as keeping a mental map of where everything is. I find that with fewer possessions, there is less to maintain and diminished cognitive load. As a result, I feel much happier.