If you have the discipline to maintain a workout regimen, then there's a good chance you're also, at least occasionally, strong-willed. You feel that you know your own body and its needs and wants. Perhaps your more mentally strong that the average person. All of those things are probably true, and yet ignoring the principles of good nutrition before, during and after exercise ultimately leads to unpleasant experiences.
Just as Dick Beardsley became hallucinogenic during his marathon, other runners have been incapacitated during important races by stomach upset, vomiting or simply lack of energy. The most-seasoned and highly trained athletes in the world can share stories of "hitting the wall" in a marathon. Since, as previously mentioned, the muscles and liver only hold about 2,000 calories, most runners will run out of fuel at the 20-mile mark if they haven't fueled-up periodically with water, energy drinks and/or energy gels. At that point, the race becomes a very difficult mind-over-matter battle. It's particularly difficult because the brain thrives on glycogen -- something you have barely any of at that point.
Other athletes may ignore the 30-minute window following a tough workout and find over time that their rate of improvement isn't matching their peers. That's why some coaches even factor the time it takes to eat a healthy meal or snack into the week's total training hours. It's that important [source: English].
An elite athlete or a weekend warrior may survive a grueling event without paying proper attention to the role of good nutrition, but they won't reach their optimum efficiency and they'll periodically find it difficult to enjoy the experience fully.