A yoga instructor from NYC says, "We breathe primarily through one nostril for 90 minutes to two hours then shift to the other. Breathing through the right nostril makes us alert, while the left nostril relaxes us."
That made me thing about how when you have a stuffy nose, it throws you all off. I was sick last week and that might explain why I was so tired. I had a stuffy nose most likely a clogged right nostril which then led to my sluggishness. I'm feeling much better now so they both must be back in business.