It takes currency to make decisions. And each day we’re only allotted so much of that currency. It’s important not to waste it on frivolous decisions. Utilize your natural energy moments (for many of us that’s early in the morning) to make those important decisions. Don’t check off a few emails, but rather make the yes-or-no sign-off on the important project.
When that capital is used up, that’s it for the day. The best thing you can do is get some rest and wait until tomorrow.