In baseball there are magic numbers which indicate the number of wins needed by a team to win a division. I know that's not a full explanation, but Dave can help me out in the comments.
My magic number for the past two weeks has been 3. That's the number of miles I have run since September 15th. Last week I was sicker than a dog (and still am) and in addition, I have returned to college which interferes with two days of running per week. Yesterday I worked 10 hours which kept me from running because I had too much homework to do for class today. My marathon is in 3-1/2 weeks and this is supposed to be my highest mileage week. I don't think 3 miles is going to cut it.