Most elite marathoners don't talk about poor workouts, they focus on what went well in the workout. If runners, who tend to want perfection 100% of the time, can learn to stay positive while they're pushing through the difficult parts of training, they'll build their confidence and see better performance results. Sometimes, the only way to learn where your personal strengths and limits lie is to make a mistake. How do you know how far you can push yourself until you push yourself just a little too far? That kind of experience helps you find your limits and gain a better understanding of what you can do, both physically and mentally.