For me, de-cluttering my schedule (my life, really) had to come before de-cluttering the stuff would "take". Uncounted times, I went through and did the throw away/donate thing, and it just built up again. But even when my house was simplified, my brain felt cluttered.
Finally, I realized the clutter was more a reflection of my mood than the cause. In the last year, I have dropped several scheduled weekly activities, cut back on gardening, lost several pets (died of natural causes and were not replaced), closed one home business, and lowered my expectations of myself in general. I still work full time out of the home, volunteer teaching ESL 2-3 hours a week, serve on a couple citizen's advisory boards, give my teens rides all over town, visit my elderly Mom at least a couple times a week, grow herbs and tomatoes in pots, knit when I can, and read a LOT. I am still busy by anyone's standards. But I have cut back enough that I don't feel rushed and frazzeled all the time.
I love cooking all day Sunday to have dinners ready for most of the coming week. I have simplified grocery shopping to once a month, supplemented by trips to the produce market in between (never crowded like the big supermarket, and fewer, or at least healthier, impulse purchases). My kids and I love antique/junk shops, but we have learned to consider them as museums, rather than shopping venues. We often spend a day shopping, but never buying. Same with the local outdoor craft market - we love the county fair ambiance, live music, artists at work, but only bring enough money for lunch. Since the Dumplings are full-size teens, we rarely have to buy new clothes (no one outgrows anything any more). I use my Kindle, so I rarely buy physical books. So maybe we really are bringing less in. But it hasn't been a conscious effort to change.
These days, my home seems less cluttered, or at least it bothers me less. There is still some extra junk around. I would like clear countertops in the kitchen, and the laundry room to be tidy. Ain't gonna happen! It feels like my mind has more space, so a pile or two of books and papers on the dining table is less intrusive. I hope the tone of this post isn't preachy - I didn't mean it that way at all. My take on the whole de-cluttering issue is that our lives have gotten so cluttered that the visual, physical clutter is a symptom, not the cause, of our over-stressed, over-cluttered lives. I hope I can be forgiven for veering from the direction this thread was taking. Feel free to ignore my philosophical musings.