I heard a knock at my door a minute ago. I had just gotten up to answer it when Marty walked in and immediately began copiously apologizing. Marty, if you're reading this, let me explain something: you only need to apologize when you do something wrong. Knocking on your own door is silly, but it isn't wrong.

Of course, I count myself lucky that my roommate is excessively nice rather than inconsiderate to any degree.