I think he just very rarely has a moment when he’s just really done. Which is probably because he’s mostly worked on things that he wanted to be working on.
I find this mindset easy to replicate when working on my personal projects. Effectiveness may drop a bit after 1am for obvious reasons, but otherwise any hour is much like another.
The problem comes when trying to get yourself to do something that you don’t really want to do, or when you need to deal with the umpteenth time someone broke the same system due to the same mistake or the third discussion in a day where people miss the obvious solution. You can only have so much of that in a day before you mentally check out.
I believe working on something you really want to do is even just one variable. There's also stuff like:
1. Do you have enough ownership to at least sit at the table when it's decided what exactly you work on and how you do it? Can you affect strategy, goals, priorities, timelines and design?
2. Do you reap at least part of the reward (financial, appreciation, status)? Does it feel fair compared to what others get out of it based on their contribution?
3. Does the actual day to day work involve sufficient things that energise you, and few enough things that drain you? Do you have the power to delegate the latter to at least some degree?
I've never met an employee who can answer all of these with yes, but they're crucial for getting things done in a truly motivated and successful fashion, at least for me. Employers don't typically give up more power/rewards than they feel they have to, though.
Ever since I went independent, I have a lot of this. That power over my own work and fortune is a phenomenal motivator, and I really enjoy work these days. I know I can work less if I feel like it, it's my decision. I can only imagine how much _more_ of this Carmack has, being rich, successful and highly respected from a young age. I don't know him, but I'd give him the benefit of the doubt and say he must honestly have no idea what it's like to not have that.
I find this mindset easy to replicate when working on my personal projects. Effectiveness may drop a bit after 1am for obvious reasons, but otherwise any hour is much like another.
The problem comes when trying to get yourself to do something that you don’t really want to do, or when you need to deal with the umpteenth time someone broke the same system due to the same mistake or the third discussion in a day where people miss the obvious solution. You can only have so much of that in a day before you mentally check out.