The joke's on me: as a consultant I've been semi-working/semi-retired my whole career. The work is nearly always new enough that I have to immerse myself into it. After it's done, I might get a breath, or I might have to plunge into something else. When working hard I have to cancel stuff I really enjoy, or simply miss it. Hate that!
I'm working my brain to its limits through Monday at 11.59 pm, when we deliver the grant.
For a number of reasons, I let yesterday be a drift and low-focus day. Caught up via email with a few friends, and took a long bath.
Today, refreshed, I'm back on task.