In my family, we have an ongoing joke because my sister absolutely will not touch a mug with even the faintest coffee stain, even if the cup is clean and she's planning to drink coffee out of it.

Your view of coffee mug stains -- like that other famous glassware optimism metric -- is also a litmus test for your view on ...

It happens faster than you think: a careless moment at the breakfast table or a rushed grab for the cup — and suddenly, ...