I was scrolling through the comments section of a popular blog and someone mentioned Antaiji's gnarly schedule of 14 periods of 50 minute zazen sessions. They said they didn't think they could do it.
For the first time during the last sesshin I sat through from 4:45am to the next day around 12:30pm. It was about 34 hours of pursuing zazen. I took two naps during that 34 hours, both within the first 12 hours- one after breakfast and one after lunch. The last scheduled period of zazen ended at 9pm. After chanting our refuges, I took a shower, drank a bowl of tea, and returned to our dimily lit Zendo- some others were already sitting.
I think there are sudden or gradual successes to sitting all night. I'm calling success the ability to walk the next day without pain and a mind clear of trauma so that you might want to sit again. I'd heard of our ancestors doing this Yaza, late night sitting practice, but it took me 10 years to approach it; others took it on in the first 3 months of practice. What was important to me was entering into this practice with a spirit of inquiry, self care, and diligence. All this to inspire myself.
What's interesting is that as I recall my night of Yaza, I didn't have any pain, I didn't have any boredom or frustration come up. I did laugh. I did cry. I was very cold, shaking at one point. I took a break once an hour to go sit by the fire and drink some tea for 10 minutes. Getting up once an hour is very important to me. Earlier that fall during my first day of Tangaryo I sat for 6 hours straight without changing my posture or refolding my legs. While it didn't hurt during the sitting (as most things were numb) when I tried to get up, I couldn't. When everyone sped off to lunch, I was stuck, leaning against a wall. It was pretty embarassing. From that day on, I switch my legs every hour and that seems to be just enough.
However, I can remember sitting sesshin at New Orleans Zen Temple and feeling sick to my stomach with pain. I remember screaming inside my head. And there only 9-12 periods of Zazen were expected each day. What changed? Did my body get "better?"
I think I stopped clenching. I've always sat in full lotus but how I sit in full lotus now is not how I sat in full lotus then. Now, I fold my legs and let them rest on each other; then, I use to grit my teeth trying to keep them from slipping. I worked from my head and my muscles. Now I don't have anything to prove- if my legs slip apart, who cares. Oddly, they don't slip apart anymore. I used to have all kinds of strange rituals to keep them from slipping, like not showering and licking my hands (quietly) and moistening my calves so maybe they'd stick together! I had this weird tick for years. My teacher must have seen, as he saw everything else, and was quick with the kyosaku if your back started to hunch.
My approach to sitting these days if very gentle. If one knee feels sore, I'll fold the other one first to give it a break. These breaks might not seem like breaks but I suspect that we set the parameters for what a break is and the mind will except any gesture if we assign that gesture the value of relief. Next relief is half lotus.
And what for? Absolutely nothing. If you go into Yaza or any period of Zazen looking for something- peace, enlightenment, or some magic power, what you'll find is an empty house full of moonlight and you'll be standing there like a silly thief. However, it's nice to find an empty house in the moonlight. I remember my night of Yaza fondly; those grueling approaches to Zazen in my earlier days still turn my stomach.
I don't think it takes 10 years to figure this out. I think you could do it right now. It's common sense! Don't push so hard or you might tear open. Just be patient and gentle with yourself. Don't be a hero. Just sit and watch the blue eye of dawn turn into the dark eye of night. It will feel like the whole Zendo is chest and lungs and breathes for you.
You just do it because it's your practice. I'm convinced that Zazen is what was really happening way back then when we were hunting and gathering. I'm convinced that you are Buddha and you're not learning how to become Buddha, but sitting as remembering who you really are.