The other great lie we tell ourselves is how long we can work productively in a day.

My boss of many years knows he can get a solid 6 hours of productive programming work from me in a day. Any more, and the quality starts to drop and with it my productivity. It's pointless doing an hour of "work" that takes another 45 minutes to fix the next day.

While I'm sure there are people that can do 10 hours of solid development work, I don't think there's that many of them, and I know I'm not one.