Here is a great article from Real Simple on Clutter-Busting secrets of the pros.
One of the tips to to pretend you're moving... here are some moving experiences of my own.
As a former military "brat" I moved every three years as a child. I recently returned to the United States after living in the United Kindgom for six years, what does this have to do with the price of eggs in China? Well, my point is that while moving to a new place is an AMAZING time to get rid of stuff you've been holding on to for way too long.
In England I lived in a three bedroom house with an attic, garage, laundry room, and back storage room. When I moved to the States, they put all of those belongings in a one bedroom apartment. FIVE crates full. (A crate is basically the size of one of the PODS you see sitting in Lowes or Home Depot parking lot) The sad thing is that there was only two of us, no kids, and 4 cats. We had sold most of our furniture before we left, we also donated a TON of stuff, gave stuff away, and consigned items at a thrift store...and we still had five crates. Before we moved I went through everything in the house over three times just to make sure I was keeping everything that I loved.
We still had so much stuff once we started opening boxes we thought, WHY DID WE KEEP THIS?! So we did a mega-purge, I mean it was one box at a time unwrapping and separating things into KEEP or DONATE boxes. By the time we were done, I think we had done five or six car loads (with the seats down in a Toyota Matrix) to the GoodWill. We went through things so fast, it was a Yes (keep) or No (donate). What a relief to get rid of all that stuff, we didn't try to sell it, we wanted it gone. And once we did that, we then realized what was truly important, and what was not.
So if you've been living in one place for over two years. Pretend like you're moving, look around and evaluate what you would like to take with you and what just needs to go. You'll be amazed at how easy it is to get rid of things once you have this mentality. Start at one area of the house and get to it! Once you get started, it really becomes addicting! :) Turn on some music and get moving...(no pun intended!)