Sleeping late on Sunday morning: Good. Working all day Sunday on spreadsheets and reports: Bad. Or at least, Not Good.
The plan was to spend a couple of hours getting caught up on some of the work I've had to put off due to constant interruptions during the actual work week. That was the plan. What happened was, I found a tiny error in one part of the Big Project. Since all the worksheets are related and have to balance against each other, that tiny error translated into tiny errors all through the project.
So I spent the whole day redoing spreadsheet after spreadsheet. Some of the ones I had to do over were the very same ones I'd produced earlier in the day. Not much satisfaction in doing the same work twice in one day.
And I had to keep at it until I was sure I'd found a stopping point. If I'd left off at the wrong place, I couldn't pick it up again smoothly tomorrow. I wouldn't be able to move on, at least not without going over a whole day's work. I think I stopped at an appropriate place, barring the usual epidemic of disruption, intrusion and disturbance.
So I spent the whole day doing something that offset any benefit from sleeping in this morning. It was tedious, frustrating work, and it left me with a sore back and bleary eyes. But it's that much closer to being done, which could turn into free time somewhere down the line.