This is kind of drastic, but I think sometimes "what would I do if I only had "x" number of years to live? Or, only one year to live? Well, we all have a finite time to live, but what if that end were imminent? Sometimes this helps motivate me and I ask myself these kinds of questions:

-- do I want to leave this earth having this mess as my legacy?
-- what about all my unrealized plans?
-- what about my children and all of the things I have promised them?
-- what will their memories be of me, will it be of my "stuff" or of me as a person and the things we did together?
-- what about the people going through my things when I am gone, what will they think -- will they laugh at me, throw everything out w/out regard to value?
-- what can I reasonably accomplish right now to make a difference in my life?
-- what is the most important thing that i need to address right now that does not involve aquiring something new or bringing something into the house?
-- how can I make a positive change right now to move towards my goal of a less cluttered environment?
-- what are my hopes and dreams?
-- can I really expect to finish all these projects? if not, which ones do I love to do? which ones can I let go?
-- when will "someday" come?
-- perhaps that someday is now!

And, then I start. I start in a small corner and work outwards from that spot. Sometimes I jump around, although, a professional organizer said this isn't good. But, sometimes I do it anyway. I always try to go back to where I started, though, and I try to finish the small task that I started. Sometimes I move quickly and sometimes I move slowly, but I move. I move and try to make decisions quickly and make progress. I try to keep focused on a long term goal(s) made up of small short term goals. What has to happen to make that long term goal a reality? I try to not get overwhelmed and focus on that one area -- that one short term goal. I sort "like with like" and keep moving. Sometimes I take a break. But, after that I keep going. The key is to get up and move and start. Somewhere, just start.