Breathing is essential for life and seems fairly automatic. However, when we are stressed we often will hold our breath [briefly] and then have shallow and more rapid breaths. Our brains are preparing us for action to avoid some danger. Often, there is no real danger, just our anxious or feaful reaction to something that might remind us of a past dangerous situation. Our breathing change indicates that we have shifted into crisis mode and the stress that goes along with this. If we can keep our breathing calm and even, we will be calm. Many different spiritual practices promote relaxed, deep breathing as part of their meditation practices.
Learning to breathe more slowly can help us to calm down. Of course, when we are stressed and worried, it can be very difficult to calm our breathing. Focusing on making our hands and feet feel warmer can help us to feel calmer. This requires that we focus on our hands and feet, seeking a sensation of warmth in them. If we do this, our breathing will automatically be calm, without having to focus on our breathing. Then, during times when we are not feeling stressed, we can practice taking slow deep breaths while being aware of the air moving through your nostrils and into your lungs and out again. Focusing on our breathing and just being aware of it can help us to feel calm and not worried. Exhaling more slowly than you are inhaling can add to your sense of being calm and relaxed.
If we just breathe, we'll like it.