Letters of Note is a site that collects "fascinating letters, postcards, telegrams, faxes, and memos." There's a letter from Pixar director Pete Docter (Monsters, Inc., Up) originally posted last summer, but which I've seen doing the rounds again recently.
Mostly, people are picking up the closing line: "As John Lasseter likes to say, our films don't get finished, they just get released" - a common refrain from artists - but it's an earlier line that jumps out at me:
It takes a lot of work (and rework, and rework and rework) to get it right.
Related reading: The Vertical Slice