I was talking about this with someone recently that long lasting changes are usually as a result of some major event or catastrophe which is why resolutions never seem to work out. There is no real impetus behind them. Granted I just took Schumpeter's concept of creative destruction and applied it to real life, but it makes sense, at least to me.
Also, I saw this thing on FB that I think would be pretty awesome. Instead of resolutions, start with an empty jar and as you go through the year you write down good things that happen and drop them in the jar. That way at the end of 2013 (December 31st if you like) you can sit down and go through them. That way you focus on the positives and not the negatives.