It isn't the heroics during training that make the athlete. It's the consistent, tireless commitment to training. They day to day little things when nobody is looking. The quiet and consistent efforts. They build your body and mind.
But ask any runner and they'll tell you of that time they went out and "killed it" during a workout. They were in a groove. Hitting their stride. Enjoying their fitness. And they wasted it on a non-race day.
The best athletes I know go out repeatedly and hit their workouts. They show discipline. Mindfulness and purpose. Save the chest pounding for when it counts.