Quit early. As my wife and indefatibable mentor has kindly pointed out to me several times: "The job's not finished until the mess is cleaned up." So don't work up to the point where you lose your enthusiasm. Clean up lies ahead. Somebody is watching.
A case in point. This is the clean up I faced yesterday. Happy hour was looming and I was starting to tire, so I dropped the hose fitting I was working on into my parts box and got started finishing up.
Later we got out for a little evening walk around the marina.