I used to wonder why I have such a severe drop in focus after any kind of social interaction, and then I read Paul Graham's 2009 essay Maker's Schedule, Manager Schedule. I can't remember when I read it, but it resonated deeply with my own observations about getting into the zone and becoming a creative hermit just so I could get something done.
Here's some salient quotes:
Most powerful people are on the manager's schedule. It's the schedule of command. But there's another way of using time that's common among people who make things, like programmers and writers. They generally prefer to use time in units of half a day at least. You can't write or program well in units of an hour. That's barely enough time to get started.
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 know this may sound oversensitive, but if you're a maker, think of your own case. Don't your spirits rise at the thought of having an entire day free to work, with no appointments at all? Well, that means your spirits are correspondingly depressed when you don't. And ambitious projects are by definition close to the limits of your capacity. A small decrease in morale is enough to kill them off.
I once spent two weeks tracking my schedule to see how much time went into CONSUMING versus PRODUCING, and was rather embarassed to see that for every half-hour of social interaction, I needed eight times as much time afterwards to recover to the point that I could focus on doing hard stuff. Well, no wonder. I have since noticed that many productive people are very strict about their creative habits (pun intended, referencing Twyla Tharp's book there).