Right vs Left Nostril
The right nostril is your sympathetic system and the left nostril is your parasympathetic system.
So you can determine if you are more "rest and digest" in this moment or "fight or flight" depending on which nostril is more dominant.
If you need to be more creative you can breathe through your left nostril to turn on the creativity. If you need to be more logical and focused breathe through the right.