Updated April 13th, 2020.
I’ll bet you’ve seen a dialog box like this before:
Or maybe like this one:
Or this one:
You probably already know the keyboard shortcut that lets you click the Save button without using the mouse: you hit Enter, or Return. That’s great, when you want it. But what about the rest of the time? What about when you really don’t care about the document, and you DON’T want to save the changes? How can you click the Don’t Save button from the keyboard?
The answer, in almost every case, is Command-D. Memorize this one (D for Don’t is the way I remember it) and you’ll reach for the mouse a little less. That will save you a little bit of time over and over and over. Try it and see.