Comment by dietrichepp

That's conflating two different senses of fatigue. "We feel tired to prevent us from making mistakes when we have been awake a long time."

That separation of the different senses of fatigue is the core of the article. Fatigue is both a feeling and a state, which we confuse because they are connected. But you can give someone drugs, like diphenhydramine or caffeine, which change the feeling of fatigue without changing the underlying state which that feeling normally reflects.