Hmn...I would actually stop breathing and slow my heart rate whenever i'm focus on writing. Since i usually have shakey hands that i usually do this whenever i draw. Every time i get serious, i would always do this and kept me calm and slow down time. I don't usually do this since i tend to always be in a near death state.
Most notably would be that i tend to space out and forgot what i was heading with my writing, even whenever i draw, i would space out like i lost regognition of myself. Treading between knowing who i am and what am i thing.
I don't usually do this on the early days of my writing career but as the words get longer, the more space out i am.
Usually, i even forget who i am for a few minutes before snapping out to reality and take on a deep breath.