Your event, be it 26.2 or 3.1 miles, doesn't really care what you did the week before the race.
It doesn't even worry too much about the two months before that.
What is is concerned with is your frequency, consistency, and volume of miles over the long term. We're talking months to years. Every day adds up, a marathon is worth more than the sum of its parts. Every little decision matters, and the consistency of positive choices makes a difference when you get to the starting line.
Training is ...