Paul Graham has an insightful essay on the difference between the schedule of the manager, which is chunked into hours, and that of the maker, which is chunked into half-days or longer:

When you’re operating on the maker’s schedule, meetings are a disaster. A single meeting can blow a whole afternoon, by breaking it into two pieces each too small to do anything hard in… That’s no problem for someone on the manager’s schedule. There’s always something coming on the next hour; the only question is what.

I find one meeting can sometimes affect a whole day. A meeting commonly blows at least half a day, by breaking up a morning or afternoon. But in addition there’s sometimes a cascading effect. If I know the afternoon is going to be broken up, I’m slightly less likely to start something ambitious in the morning.

I try to do maker things at home, and “manager” things in the office, but as Paul observes, it’s tough to straddle both schedules.