Sure, we are always breathing, but if we aren't taking special care to increase our oxygentation levels every now and then, we could be living less than optimally. Having adequate oxygen in your body helps your body's immune system long term and helps alleviate stress and acute symptoms as well.
Low oxygen levels in your blood can lead to immediate symptoms such as
Sometimes in times of stress we tend to hold our breath more than when we are relaxed. This is the exact opposite of what we should be doing. Deep breathing is one of the best ways to lower stress in the body. This is because when you breathe deeply, it sends a message to your brain to calm down and relax. Those things that happen when you are stressed, such as increased heart rate, fast breathing, and high blood pressure, all decrease as you breathe deeply to relax.
You also need to know passive breathing gets 80% of the job done and you have 20% stale air in your lungs. This number increases in people with asthma and other chronic lung diseases.
We can remedy this with active breathing exercise: stale air out