Thinking time
gorban.org
gorban.org
If that's the case - you finding yourself with a busy brain that seems incapable of finishing any thought - Stop working and allow it some time off to tie up those loose ends.
I have found that my brain has three modes of working when it comes to creative thinking - The first is in-the-moment thinking, where and work and thinking are one - Synchronous Thinking. The second is finishing up thoughts while I'm doing something else (literally, getting the results to a thought-process out of the blue) - Asynchronous Thinking. The final one is the one described here - Exclusive Thinking.
Learning which of those to employ at a given moment (based on your workflow and mental constitution) is an artform and hard to master, but just being aware of it is already a big step.
(And not to forget - there is also a fourth one - Exclusive Non-Thinking, but that's a whole different area of philosophy and more related to general mental balance than it is to getting work done.)
I find that the thoughts come along when they want to and think themselves anyway. They laugh at my (paper) diary. I suspect that this is related to me being on the 'maker' schedule rather than the 'manager' schedule.
1) You have a complex problem that will require a complex solution, and you're procrastinating in figuring out how to deal with the problem.
2) You're coming towards a milestone in a project, and it's time to plan out the next steps and goals.
For both of those scenarios, just taking a walk with a pen and a notepad can be the most efficient use of your time. Sometimes a bit of fresh air and slow, methodical thinking goes a long way.
Basically it's scheduling a time to review and evaluate everything on your to-do list. This seems to be a forward looking "what else can I do?" variation on that.