Reformulating Plans

I am not even going to bother with the typical format for this post. The past two weeks have been much of the same. A few days a week I doubled and put in around 120 minutes. Other days, I only ran 30 minutes or completely took the day off. I was around 50 miles for each week. From Friday to today, I didn't run a step.
Part of the problem is that, despite the decreased mileage, I have been feeling very tired. My favorite part about running is being able to go out for a 90 to 120 minute run, cruising along at a quick pace, and have it feel completely effortless. I honestly can't remember the last time I wasn't hoping to just get home during one of my runs.
Another part of the problem is that I get tied up with this mindset that if I am not running 100 to 110 miles a week, I might as well not be training. It is very hard for me to get out the door on Saturday and Sunday to finish up a 60 mile week. I know it is absurd, because there are obviously training benefits from running 80, 70, or fewer miles a week, but I just struggle with motivation when I am not running as much. I think it goes back to the whole sense of purpose idea where each run in a big week is building towards a larger goal. I just don't get that feeling when I am not running as much.
My plan was to run the New York City Marathon this fall, but I am starting to think that it might be in my best interest to defer my entry for a year and run a cross country season. With work and grad school, I am not sure that I will be able to train for a marathon the way I would like and I feel like I might be setting myself up for frustration.
I am hoping that my upcoming vacation will be a good chance to get stuff straightened out a little. Who knows? Maybe doing cross country and indoor track would help me out to come back and run a spring or fall marathon in 2009.
Sorry for the pity party of a post, but it's all I've got right now.