UPDATE: Lanette shared a link to the original blog post!
It was at least five years ago. I read a post by blogger and all-around testing guru Lanette Creamer. It has stuck with me. I don't remember enough keywords to track it down but the gist of it was to imagine two testers, with let's say, way more work than they can reasonably do by a deadline.
One gets overwhelmed, frazzled, and angry. He works late hours and weekends, sighing about it the whole time, not helping out others with their questions, sleepily and grumpily doing the work he perceives is expected of him.
The other is calmer and remembers he's a member of a team. He does solid work and puts in some extra hours but not so many that he loses passion and focus. He is available to help a new tester become better. He gives updates on what he has done, and what concerns about risk remain.
And it had a "which one would you rather work with?" type of question posed at the end.
Whenever I get an extra task on top of my already-packed task list and my first instinct is to burn myself out to the point that I snap at people who dare stop by my desk with a question, I remind myself that I'd prefer to be the second tester.