Mood days
Here's an interesting idea I've been trying to figure out what to do with: it seems like some days have particular moods. Maybe because of the things you have planned that day, or other things that happened recently, or just your general mood taking form in what you do. Some days seem very productive, other days don't. Some days seem energetic, others are relaxed.
I've noticed that on the days I know are going to be very distracted, there seems to be very little point in fighting it and trying to focus. I've previously gotten quite frustrated trying to fit in an hour of focused thought between visitors and social events. The solution was presented to me by a friend: don't fight mood days, embrace them. If it's going to be a crazy distracted day, use the opportunity to knock off a lot of small tasks that might otherwise disrupt a perfectly good focused day.
Of course, the flip side is that if you're feeling particularly calm and focused, that's a bad time to start ticking off little to-dos or answering emails. And there's obviously some degree to which you can influence the mood of a day, especially if you have a lot of time to play with. But often you don't, and I think learning how to make the best of what the day has to offer is a big improvement over trying to swim against the tide.