Your nose is a sophisticated air-processing system
It filters, warms, and humidifies air before it reaches your lungs — and produces nitric oxide, a molecule that dilates your airways and blood vessels, improves oxygen delivery to tissues, and kills airborne bacteria. Mouth breathing bypasses all of this, leading to dry mouth, increased cavity risk, disrupted sleep, and narrowed airways over time.
Practice: With lips gently sealed and jaw relaxed, take slow, quiet breaths through your nose. Check yourself throughout the day.