COVID-19 and Mask-Related Respiratory Issues
The CDC may not recommend the use of N95 respirators for the general public because they can be more difficult to breathe in, but they are still the gold standard of respiratory protection for a reason. The effectiveness and difficulties of N95 respirators both lie in the fact that this type of face covering creates a tight seal around the face, usually with a built-in filter, to prevent 95% of airborne particles from penetrating through the sides of the mask. 
How Do Respirators Affect Breathing?
Although respirators are the most effective form of respiratory protection, they also restrict inhalation or inspiration (the process of allowing air into the airways of the lungs). This constriction of airflow leads to a distorted compensatory use pattern between the respiratory muscles: diaphragm, rib cage muscles, and the abdominals.  This further means that the diaphragm is unable to fully contract and the ribcage to completely expand. So the breathing is bottle-necked at the diaphragm and becomes shallow, preventing us from physically relaxing and creating feelings of tension and anxiety.   Additionally, with the roadblock at the diaphragm, the opposing muscle group, the abdominals, become under-activated and weak.  This can compound physical ailments, especially with the increased sedentary nature brought up by the pandemic, because the abdominal muscles are essential for most movement.  It is important to note that most of these issues can be resolved through maintaining physical activity and fitness as well as strengthening the respiratory muscles.
Stress and Respiration 
Because the majority of us did not usually need to wear a face mask for medical or job-related reasons, we are forced to adapt to the change. This change can be a source of added stress and anxiety.  When we become stressed and anxious, it has a direct impact on how we breathe, often in the form of hyperventilation (breathing too fast) or hypoventilation (breathing too slowly).  During hyperventilation, we are exhaling more carbon dioxide than the body can produce, which leads to dizziness and lightheadedness.  On the opposite end, during hypoventilation, we are not exhaling enough which can lead to drowsiness, fatigue, and fainting. 
Continual dysregulated breathing creates more stress which leads to additional physical and emotional stress. Too much negative stress (distress) hijacks the sympathetic nervous system (responsible for increased heart rate/blood pressure, restricted breathing, adrenaline and cortisol surges).  This can lead to these additional stress symptoms: inflammation, muscle tension/fatigue, lowered immune response, decreased metabolic efficiency and sleep issues as well as moodiness, irritability, and anxiety.
How Do You Reduce These Issues?
Because of the relationship between stress and breathing, the way we breathe is tied to our respiratory health, which, in turn, impacts how we fight off diseases such as COVID-19. To maintain optimal health, it is important to keep the respiratory muscles (diaphragm, rib cage muscles, and abdominals) strong through targeted exercises or by using a breather machine (a tool used for respiratory muscle training. In addition to the physical health component, it is all the more important to pay attention to stress, anxiety and overall breathing patterns.