The Environment Makes a Big Difference

You're not just going to go out and run a marathon. You need to work up to it. Cal mentions that some of the masters that have been practicing deep work, they can maybe go for four hours - which isn't even a full work day. So nobody would be able to fill up their entire work day with purely deep work. It's something that you really do need to block out, but also work up to as well as blocking that time out. And along your along these lines, deep work takes training.