Leftovers.
My office isn't within walking distance of anywhere to eat. That plus it's just a pain to go out. Much better and less stressful to keep working or take a short break at the desk. And then leave a little earlier from the office as a result.
My beloved sweetness and joy (now of 19 years as of September 12th) knows that it reduces my overall stress to bring lunch and almost always has something to send me off with.