Over the decades, I've found that my debugging success requires me to be (somewhat) rested - it's waiting for a spark, which I guess makes it similar to creative activities. No spark, no ah-ha moment and it's a slog. Thinking is a muscle, and like all muscles it needs both exercise and rest in proper amounts.

And, as a developer, there's always more bugs and requests than can be dealt with. We all exit the stage with a full in-basket.