Sam - I'm trying to change my mindset from focussing on one race and the short-term. I recently posted a question on RW about setting a "five year plan" and had some useful responses to get me thinking.
Now I'm going to have my dream goal, which is also welllllllll beyond my current capabilities (Good for Age, 3:15 marathon - don't laugh). I'm going to break it down into stages of what I want to achieve each year. This year is 4:20 to 4:30, next year sub 4:00 and so on (haven't decided exact time-scale yet, but I'm still loosely thinking of a five year plan - realistically probably longer. I'll start on improving speed to get to sub-4 after recovering from this years marathon (probably concentrate on 10k, then HM).
I've looked at the training required to get to sub 3:15. The amount of mileage isn't too daunting, but the speed scares the bejeezers out of me

Anyway, being fifty I may never make my dream goal, but I should get a lot fitter finding out if I can do it. It should keep me concentrating on improving long after my marathon has passed and break me out of a plateau of my own making. If all else fails, maybe I'll make good for age at 60, which is "only" 3:30

If you wouldn't mind, you can write your column about how I can write my plan to achieve all of this. Better still make it a book and send me a complimentary copy