If I have a major project scheduled for a day, my usual practice is to cancel, reschedule or reassign any tasks which are not needed for that project.
Some people regard that as unproductive. After all, they argue, I could be doing other things. Why dedicate more time than is needed for the project?
What they miss is that by doing nothing that is likely to distract my attention - be it conscious or subconscious - I gain focus and self-confidence. The quality of the time dedicated to the project is expanded and enhanced.
Gaps which might have been overlooked are spotted.
This has been my practice for many years. I've never regretted it.