I used to be what they call a "pack rat." My mother called me "Stuff Girl" (no kidding) and she likened my bedroom to a museum, a collection of objects meticuously displayed, covering every horizontal surface and most of the verticals. Then one year, near the end of high school, something just snapped and I threw it all out. Gave away whatever I could. I gleefully stuffed things into giant garbage bags and kicked them to the curb, to charity, to my friends, whoever would accept them. I hardened my heart against the pitiable faces of even my favorite stuffed animals, and did away with the trappings of my childhood. I am a minimalist, you see, and I have a very particular aesthetic. I like my things functional and attractive, and anything superfluous, tacky, kitschy, or nostalgic must go.
I repeated this performance as needed, obeying the mantra, if you don't need it or want it or like it, don't keep it. The goal was to keep mobile -- I should only keep what I would be willing to personally carry from residence to residence. Anything that will spend its life in the back of the closet may as well move out for good. Unwanted gifts were disposed of with only moderate guilt. Even most of my school artwork was mercilessly dispatched (I told myself that I wouldn't regret it, but I may have been wrong). I may occasionally miss an item or two that I've gotten rid of, but overall, I feel mercifully free. Each and every thing that I own is an essential and integral piece of my daily life, something I appreciate and treasure. Everywhere I cast my eye it falls upon beauty, simplicity, and harmony. There are no more skeletons in my closet, just clothes and luggage and spare blankets and posters waiting to be framed. Useful things. Out of sight, but needed.
That's my advice to anyone struggling with too much stuff: renounce, renounce, renounce.
Just be sure that you won't regret it.