My friend and running partner for over 35 years, Brian Tonitis, once said, "It only counts when you pay your entry fee."
Training is all about challenging oneself, pushing the limits of one's ability, walking the tightrope without falling off.
When I focus on a big race, or when I coach others to do so, I usually break the training period down to a 10 or 12 week segment. During that time, I emphasize "quality miles." Intense long runs and weekly speed workouts are, in my estimation, the keys to success, from the 5K to the marathon distance.
Actually, when I design a 12-week plan, it begins 13 weeks before the big race, because as important as the training may be, the final week before the race is equally as important, because that is the time to taper.
Physiologically, any workout conducted within two weeks of your big event will not significantly improve your performance. In fact, if you choose to pound out a fast 20-miler ten days before your marathon, there's a good chance you will negatively affect your marathon time. Besides, by the time you are a week out from your race, "The money's in the bank."
Make sure, then, that you don't leave your race on the road, during a training run, in the days leading up to your event.
If I'm running a marathon or a half marathon, my last significant workout will be run eight days before the even. For a marathon, it might be a 10-12 mile run, at a gentle pace. Remember, the work has been done.
I'm running the Philadelphia Half Marathon on Sunday, On Saturday (8 days prior to the race) I ran a 7-miler. Now, I'm tapering. 5 miles yesterday, today and tomorrow. 4 on Wednesday and Thursday, 3 on Friday, and 2 on Saturday. All miles will be easy. If you choose to take off and rest the day before the race, that's fine
The objective is to feel rested and refreshed when the gun sounds to start the race.
Remember, workouts matter. They get you there, but it really only counts when you pay your entry fee.
Train hard, but as the race nears, taper easy.