There’s no “right number” of houses to see or job candidates to interview. One rule of thumb is to keep searching for options until you fall in love at least twice. If you’ve only identified one good candidate for a job, for instance, you’ll have the strong urge to talk yourself into hiring her, which is a recipe for the confirmation bias. You’ll start to make excuses for the flaws you see: She asked us not to call her old boss for a reference, but that’s probably okay, because the boss sounded like a real jerk …
