Paul Graham contrasts Good and Bad Procrastination:
What’s “small stuff?” Roughly, work that has zero chance of being mentioned in your obituary. It’s hard to say at the time what will turn out to be your best work (will it be your magnum opus on Sumerian temple architecture, or the detective thriller you wrote under a pseudonym?), but there’s a whole class of tasks you can safely rule out: shaving, doing your laundry, cleaning the house, writing thank-you notes — anything that might be called an errand.Good procrastination is avoiding errands to do real work.
His key point:
The reason it pays to put off even those errands [which get worse if you put them off] is that real work needs two things errands don’t: big chunks of time, and the right mood. If you get inspired by some project, it can be a net win to blow off everything you were supposed to do for the next few days to work on it. Yes, those errands may cost you more time when you finally get around to them. But if you get a lot done during those few days, you will be net more productive.
More poetically:
People who fail to write novels don’t do it by sitting in front of a blank page for days without writing anything. They do it by feeding the cat, going out to buy something they need for their apartment, meeting a friend for coffee, checking email. “I don’t have time to work,” they say. And they don’t; they’ve made sure of that.
As Richard Hamming asked, What’s the best thing you could be working on, and why aren’t you?