Yoga uses a combination of physical postures, focused breathing and awareness to train your body to be relaxed. This is how it works:

• Physical Postures (asanas):- Holding poses and and stretching can assist relieve joint pain and muscles strain. when your body is not tensed, it naturally tends towards relaxation. Slow deep breathing instructs your nervous system to switch from fight to flight to rest to digest mode. and this slows your heart rate, lower blood pressure and reduce stress chemical. 
• Mindfulness and awareness:- Yoga helps your brain to stay in the current moment, this lowers your mind chattering or overthinking and allows you to understand and let the stress and anxiety pattern that stored in your mind and body, go off.
• Reset your Nervous system:- Some posture such as legs-up-the-wall or child's pose (Balasana), immediately calms and relaxes ones nervous system. 
• Routine & Rhythm:- Yoga's constant, flowing sequence such as, beginning with breathe and ending with Corpse pose (Savasana), teaches the body to anticipate and enter in a relaxed state. After a frequent practice your body will start remembering, how to shift into a relaxed state more easily, even you are not having proper yoga poses and sitting on your mat.

                                                              Yoga is for-sure a powerful tool to relax and calm your body as well as mind. By incorporating physical posture, breathing techniques and meditating, you can calm the body and mind, can be in more peaceful and relaxed state. and it's regular and frequent practice can reduce stress and anxiety, enhances overall physical and mental health and improve quality of life.