When you literally have too much stuff, it can be burdensome. Everything can't have sentimental value, but it is easy to be attached to what possessions represent to us. Objects have meaning and in some cases objects mean more to some people than others.
My suggestion is to clean house once a season. Give, sell or trash what you don't need or want. If you haven't used something in a year, I'm 95% sure you won't use it again. I personally try to adhere to a one in, one out policy. If I get something new, I have to get rid of something old. The concept is supposed to force me to keep myself accountable to my possessions.
I know "trimming the fat" as I say, is easier said than done for some people. N is pretty attached to his possessions. He hates letting go of, or throwing away, anything. Most of the time, this drives me nuts. But life is about celebrating minor successes. Last week, he threw out a pair of socks that had holes in them. I gave him a high five.