If you've ever had a friend or family member tell you to relax and take a deep breath during a stressful moment, know that they're onto something. And you don't need to wait for a stressful moment to happen — regularly taking deep breaths is also a great way to reduce stress. 

Breathing is one of Dr. Johansen's favorite ways to reduce stress because it's simple and effective. "Your breath will directly influence the autonomic nervous system, by the stimulation of the vagus nerve via expansion of the diaphragm causing you to relax," she says.  

Dr. Johansen notes that deep breathing exercises allow the nervous system to get in formation and help relax your body after a period of stress, according to research. 

Other research also found that learning and practicing diaphragm breathing (or deep belly breathing) decreases your blood pressure and heart rate, helping people relax and lower cortisol levels. They also found that even a single breathing practice significantly reduces blood pressure, ultimately reducing stress and allowing the body to relax. 

How to practice it: 

Box breathing is one technique that Navy Seals rely on to stay calm under pressure. Just imagine each side of a box and do the following: Inhale for four, hold that breath for four, exhale for four, and hold it for four.