Many, many times have I extolled the virtue of long runs. The physiological and psychological benefits can be found in one of my older posts, entitled On The Importance of LSD. Check it out, it's has sound research on why long slow distance is important.
However, times and ideas change, and if there was one thing I could add to that post, it would be this. Long slow running, where the distance tires you out, not the speed; makes you a tougher athlete. One that can wake up super-early in the morning and be ready to compete. One who works through the initial aches & pains of loosening up without getting discouraged or losing confidence. One who does not mind exercising for over an hour, and therefore does not mind a long 12 hour track meet. One who has the mindset that a goal must be reached, and nothing will stop them from reaching it.
Racing well is not just physical task, it is a mental one too, and long slow distance runs, where you deplete all your glycogen reserves, are a crucial aspect to being fast. Some people disagree with me, but there are no such things as "junk miles". Any type of running is better than no running, so make that your goal for this weekend! Lots of time spent running!