"Have nothing in your house that you do not know to be useful, or believe to be beautiful." - William Morris, Architect, instigated the Arts & Crafts movement in the 1860s.
You love your things. That shirt you never wear brings back great memories. Those dusty boxes in the basement are full of former glory. The things you spent good money on, but never used are taunting you, but you can't let them go.
It's time for a two-pronged attack on clutter.
Prong One: Guard. Don't acquire things that you don't need and that you won't use regularly. It's easier to guard against clutter at the gate than it is to get rid of it once you've allowed it into your life.
Psychologists tell us that things can only make us happy for 6-12 weeks. After that, it's just more stuff.
The pain of losing something you had is greater than not getting it in the first place. That's one of the reasons you will find salespeople putting something you're considering buying into your hands early in the sales process. It's tough to give it back.
This strategy will save you money as well, because reducing the things you buy will save you money without reducing your long term happiness. If you want to spend money on happiness, go for experiences instead. If you still want to buy stuff, write it down along with the date. If you still want it in 30 days, it might be something worth buying.
Prong Two: Purge. Some of your unused things might fetch some cash in the right market. It takes time and effort to sell these things, but can be worth it.
Sometimes, though, just getting rid of the stuff can be valuable enough. Donation bins for clothing are commonplace. If letting things go is hard, take pictures of what you're getting rid of. That way you can keep the memories, without having to warehouse the stuff.
Get rid of the easy stuff first, but don't be tempted to fill up the newly empty space with more stuff.
Don't feel like you have to do it all at once either. This is incremental. After the first round you'll notice more things that need to go. Proceed in waves.
Guarding against new clutter and purging the things you don't use anymore will free up space, both physically and mentally, for you to concentrate on what's important to you now.