Defining done before you start

Most unfinished work was never given a finish line. "Improve the essay" has no end. "The essay is done when it is within the word limit, every claim has a source, and one other person has read it" has three. Without a definition, work simply continues until the deadline takes it away from you.

Write the definition at the start, while you are clear-headed, and treat it as binding. The version of you at ninety per cent is tired and either wants to stop early or wants to keep polishing forever, and neither is a good judge of whether the thing is finished.