Your breathing is the wave that carries you through a session, and it’s also your portal to the meditative state, which is why as long as you are still in your breathing you are still in your yoga practice.
What happens to a lot of us is that the intensity ratchets up, and of course our heart rate and blood pressure ratchet up right along with it, and the outcome is that going as deeply as we would like into a pose while maintaining the same rate of rhythmic breathing becomes a real challenge, sometimes an impossibility.
If you have to choose between focusing on a pose that has gone awry and therefore letting your breathing get away from you, or focusing on keeping your breathing in control and therefore letting a pose get away from you, always choose your breathing first. It’s the key to your practice, both on your mat and in the rest of your life. Getting it right will make everything else fall into place in time. Put all your attention into keeping your Ujjayi breath slow and rhythmic and no matter what else is happening in your body you will still be fully in your yoga practice.