MHO Brain Freeze

I keep observing this happen where I do my thought download, break down my tasks into smaller pieces, but when it comes time to put them on my calendar I freeze up. I observed I go into overwhelmed/confusion with thoughts of :
-I don’t know what to do,
-I don’t where to start
-complete blank/ frozen

Which then leads me to want to physically get up move around, (like a little kid with ants in their pants.) I end up walking around my house aimlessly, getting a snack, or looking at my calendar again and overthinking about something getting caught up in an email and not staying on task to put the items in my calendar.

What do I do when does brain freeze happens to force myself to put something in my calendar?