If, like me, you work in the software world, you will like the following from Joel Spolsky’s article on software engineering and schedules at Inc.com:
Software development takes immense intellectual effort. Even the best programmers can rarely sustain that level of effort for more than a few hours a day. Beyond that, they need to rest their brains a bit, which is why they always seem to be surfing the Internet or playing games when you barge in on them.