I can't explain this, but try it if you're generally one of those Type A hard-driving mastery-oriented maximizing always-work-a-lot types.
(I'm one of those.)
Ok, try this.
Next time you have a day where you did okay earlier but later in the day things are kind of just dragging along, do this:
1. Recognize it.
2. Decide to just chill and do whatever for the rest of the day.
3. Mentally say something like, "I'm just going to chill and a have good time for the rest of the day. Not going to do anything in particular, just enjoy myself."
I can't explain it, but the shift is incredible.
It's like, "This sucks, the day is grinding along, why aren't things happening...?"
Then... shift... CLICK.
Oh. Having a great time all of a sudden. Ironically, able to do a lot of productive stuff. Or just read, or think, or enjoy the day.
I don't know if this would work if you have must-do's that aren't done. Maybe not. But if you got the core baseline performance you need, and you're just in silly-maximizer mode and making yourself miserable while getting nothing done, give it a whirl:
"I'm kind of grinding along. I'm not going to run down any production for the rest of the day. I'm going to enjoy myself, pressure off, kill it tomorrow."
... shift... CLICK... happy.