What is ego depletion Baumeister willpower research?

Example: You have spent three months building the perfect personal operating system. Your task manager is immaculate, every project has clear next actions, your calendar is time-blocked, your decision heuristics eliminate trivial choices, and your information diet is curated to exactly what matters. On paper, your throughput should be extraordinary. On Monday morning after a full weekend of recovery, it is. You clear your deep-work block in ninety minutes, ship two deliverables before lunch, and make three consequential decisions without hesitation. By Wednesday at 2 PM, the same system produces almost nothing. You stare at the same document for forty minutes. You re-read a paragraph three times and cannot extract the meaning. You open your task list, see the clear next action, and feel a physical resistance to starting it — not confusion, not ambiguity, but a dull heaviness that makes every cognitive operation feel like pushing through wet concrete. Your tools are the same. Your processes are the same. Your information inputs are the same. What changed is you. You slept five hours on Monday and Tuesday, skipped lunch both days, and ran six consecutive hours of meetings on Tuesday afternoon. Your system is perfectly optimized. Your energy is depleted. And a perfectly optimized system running on depleted energy produces roughly the same output as no system at all.

This concept is part of Bottleneck Analysis in the How to Think curriculum.