If you could only use one productivity mantra all day, what should it be?

I considered: Single task as much as possible in everything you do.

Multitasking is bad for productivity.
Keeping an eye on your phone while trying to focus.
Switching between tasks constantly.
Thinking about something else during a conversation.
Taking on many projects simultaneously.

Asking The Most Valuable Question throughout the day was another contender:
‍What is the most valuable way I could be spending my time right now?

But one requirement precedes all others:
‍Start from a place of calm.

A disturbed mind affects everything you do.

Such a mind
Is less creative;
Sees troubles that don't exist;
Responds in ways you don't want;
Can't concentrate;
Goes around in circles.

So before you act, check your mind.

Is it calm?
If it's not, consider what's needed to reach that state.

A walk?
A deep breath?
More information?
Less information?
Focus?
A break?
Sleep?
Vacation?
A talk with a friend?

Provide whatever your mind needs to start from a calm place.
Only then proceed with what you need to do.