"Yeah. Mental performance degrades as you work longer hours in a day, and some things rely on peak mental performance. There are, though they are rarer, four-hour industries that pay higher than the ten-hour ones, and the people in those industries don't try to do more than four hours of work per day because they'd start making mistakes."
"I've been stupid, even if you want to work long hours for great profit - which, I mean, we're all young, and it's not like I've been keeping myself down to ten hours - I should still be trying to schedule the peak-dependent hardest mental work that takes a Fox's Cunning earlier in the day. I have been doing that with myself and learning wizard spells, which is more straightforward, during the evening, but I wasn't properly optimizing that for everyone else."
"And you still need any time to think about things on your own or just catch your breath."