I think the BIGGEST thing, and something I wished someone taught me at a younger age, was the concept of self control in recovery. Just because you CAN run every day at 6 min pace, doesn't mean you should. This is true even if you are getting your workouts done. At some point you will pay the piper, and that might just be on race day...
Ding, ding, ding . . . ! Exactly!
This should be drilled into every runner's head constantly until they actually do it. I heard it before, but it has taken a long time to actually force myself to work that way.