By now, it should be fairly obvious how vital breathing is to our survival. That's why we’re equipped with two breathing apparatuses: the nose, first and foremost, and the mouth, secondarily. There are times when breathing through the nose is essential. However, there are also times when it is not possible, such as when you have a cold and a stuffy nose. Without the mouth to breathe from, you would suffocate.
In many athletic events, such as swimming, mouth breathing is the only feasible way to get air. However, nasal breathing is far more relaxing and healthier because of the filtration system in the nasal cavity, which filters particles, bacteria, pollen, dust, etc.
I have many restless nights trying to sleep with a stuffy nose, forced to breathe through my mouth because I couldn’t clear my nasal passageway due to a cold or allergies. I noticed how poorly I sleep when I can't have unobstructed breaths through my nose. I sleep with a greater degree of anxiety, and my dreams are anxious as well.
I try to take long, deep breaths through my nose while sleeping and exhale slowly through my mouth to feel better. One night, I woke up and simply propped my head on a pillow differently than usual, and my nasal passageway cleared. I started breathing through my nose again immediately, and I felt better and more relaxed mentally.