Quality Workout Tip:
Here is a practice I have been doing with my runners that helps in getting the maximum benefit from the quality workouts without over training.
Use an effort scale for each workout. This is an easy scale from 1 to 10 with a 10 being a maximum race level effort.
Make the primary goal of your quality workouts to do the workout at no higher than 8 on your effort scale. Any quality workout done at an 8 is considered a win regardless of the time.
I still set certain time targets or ranges for a workout so that they have a pace to shoot for, but if hitting that pace requires an effort level for the workout beyond an 8 then they should back-off, hit a little slower time and preserve the 8.
For my younger runner especially I make it this a hard rule. No workout beyond an 8 and we both have input into the actual effort level used (so they aren't tempted to fool themselves).
This helps mentally taking some of the pressure of key workouts and allows some good solid quaility work to be done while not leaving the race out on the track in a workout.
It also helps my runners remember that there is no one workout that will make them champions, its a long series of workouts done at the right effort level that will make them champions over time.