‘Errands are so effective at killing great projects that a lot of people use them for that purpose. Someone who has decided to write a novel, for example, will suddenly find that the house needs cleaning.
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.’
Paul Graham also wrote on this.