Yoga generally referring to practicing postures to gain strength, flexibility of whole body. Practicing yoga has to be in a safe manner to avoid any injuries. Patience is utmost important during the practice. Quoting from one verse in Yoga Sutra: Sukha, Sthiram, Asanam meaning Posture should be comfortable and stable. Imagine you are struggle during the practice, not only you are not relaxing your muscle but you might cause tension in the entire body and not able to enjoy the real benefits of the asana.
Breath in, raise your both hand up, breath out, bend forward. This is like a mantra during most of the yoga classes.
Obviously, Yoga and breath is inseparable, well, life IS BREATH! Period.
By breathing correctly, one can perform better during asana, you can also hold longer in difficult posture just by focusing on your breath. Breath is our life force, through breathing correctly we can prolong our life. Take a look at the animals, why dogs have average of 14, 15 years of life and tortoise can live up to 100 years? Simply observe their breathing, dogs breath hard and fast while tortoise breath slow and deep.
When you able to control your breathing during the practice, you may find tremendous improvement in your postures, such as better sense of balancing, better use of strength, more extension, flexion and stretching in the poses and many more.
Proper practice of various breathing techniques will also bring benefits to your wellness and ultimately, achieving a peaceful state of mind.