Can someone explain to me how you can be productive for 12 hours on a single day?<p>When I do concentrated programming work, I can maybe do 4 hours, at best 6 hours. It seems I can stretch it when doing more mundane work when I know what needs to be done. But this time is seriously reduced when I have to think about architecture or more complex stuff.<p>The literature also point into this direction, where writers and serious thinkers do these kind of few hours (also see Cal Newport on deep work).<p>I know John Carmack said you can be more productive when you can do more easy tasks to fill up the day, but it ends somewhere.<p>I have a master degree in computer science, and during the exams, my head was full at 20:00. Nothing could get in after that. I know people who could study until 3 in the morning. But you know what, after questioning them, they didn't do shit in the morning.<p>At work, I always had great reviews and my employers loved me (I'm almost 40 now). I always felt I was slacking off because I worked too little. But then I understood, if I work so little and get great reviews, what are those other guys doing?<p>So 12 hours a day? You are just lying to yourself. Those people are slacking off like crazy, and probably can't get anything done during the day. And at the end of the day, they are angry at themselves that they didn't do shit and wasted most of those 12 hours slacking off.<p>But I am sincerely asking to prove me wrong. Is it possible to work 12 productive hours a day? I was always searching for this how some people claim to be able to pull this off. But after investigation, they never really were able to do this.