The great teacher "Homeless Kodo" Sawaki Roshi said about sleep and Zazen ...
Eat in order to do zazen, sleep in order to do zazen. This means that eating and sleeping are also part of zazen.
In other words, we must be properly fed and rested (not too much, not too little ... ours is the Middle Way) in order to sustain our Practice properly. Get rest.
Of course ... that is if we can. Sometimes, more easily said than done these days. If you do find yourself unavoidably tired (because of your 3 jobs), but also feel your Zazen unavoidable (which it should be most days), follow the words of Uchiyama Roshi ...
That is for day to day practice. Find the time which suits you best, morning or evening maybe afternoon, and sit consistently then. Sit with a bit of sleepy Zazen when it happens. If too sleepy, and literally falling of the Zafu, go get some sleep.Another time you might be tired. Then you have to remind yourself that you are practicing zazen right now, and it is not the time for sleeping. This is correcting your attitude, correcting your posture, really opening the eyes and returning to zazen. This is called “Awakening from dullness and fatigue.”
If in a Sesshin or other intense retreat, it may be a somewhat different story, and we may wish to push ourselves a bit harder (pushing hard with nothing to attain ... but non-attainng!), Remember the words and actions of Master Dogen's teacher, Master Nyojo (Ryujing)
In bed by 11, up for Zazen at 2:30! Rujing seems like a heck of a drill sargent at the Dharma boot camp!When staying at Tendo Monastery in China, while the old master Nyojo was abbot there, we sat zazen until about eleven o’clock at night and got up at about half-past two to sit zazen. The abbot sat with the assembly in the sodo, never taking even one night off.
While sitting, many monks fell asleep. The abbot walked around hitting them with his fist or his slipper, scolding them and encouraging them to wake up. If they continued to sleep, he went to the shodo1, rang the bell, and called his attendants to light the candles. On the spur of the moment he would say such things as; “What is the use of sleeping? Why do you gather in a sodo [monk's hall]? Why did you become a monk and enter this monastery?”
One time, his immediate attendant said, “The monks in the sodo are tired and sleepy. They may fall ill or lose their aspiration because of the long hours of sitting. Please shorten the time of zazen.”
Angrily the abbot replied, “We must never do that. People without bodhi-mind who temporarily stay in the sodo would sleep even if we sat for only half an hour or less. Practitioners with bodhi-mind who aspire to practice are happier the longer they are able to sit and therefore, practice much harder. ”
http://global.sotozen-net.or.jp/common_ ... 02-25.html
But on most days ... the advise is to get sleep sufficient to allow Zazen. It is best to sit in the mornings upon awakening, or at night just before bed. But you can pick another time when not so tired too. Then, take a bit of the sleepy zazen when it happens, if its too sleepy go get some sleep and sit on waking. If falling asleep during Zazen (although discouraged), just do that ... I promise not to beat you with my slipper (and hopefully it will not happen most days ... even Jundo falls asleep on the "sit-a-long" now and then, if you look closely! ops: ) .
If you sit Zazen and it is ZZZZzzzzz, just perfectly ZZZZzzzz!
By the way, just adjusting the posture, opening the eyes a bit more and taking some breaths can help. I stretch my neck just a bit when tired during Zazen, and it seems to help ... as if a tiny string running from the top of my head to the ceiling were given a light tug. Or, one can return to following the breath for awhile. Monks in China and Japan have always had a close relationship to tea and caffeine (in moderation!). At more Sesshin I have attended in Japan or the West, tea and coffee (in moderation!) are always somewhere around.
Master Keizan wrote (in his Zazen Yojinki about the year 1400) ...
A bit of Kinhin, for a few minutes, can be good when very tired.Although we shouldn’t be too anxious about bodily comforts, inadequate clothing, food and sleep are known as the "three insufficiencies" and will cause our practice to suffer. ...
... If dullness or sleepiness overcome your sitting, move to the body and open the eyes wider, or place attention above the hairline or between your eyebrows. If you are still not fresh, rub the eyes or the body. If that still doesn’t wake you, stand up and walk, always clockwise. Once you’ve gone about a hundred steps you probably won’t be sleepy any longer. The way to walk is to take a half step with each breath. Walk without walking, silent and unmoving.
If you still don’t feel fresh after doing kinhin, wash your eyes and forehead with cold water. Or chant the Three Pure Precepts of the Bodhisattvas. Do something; don’t just fall asleep. You should be aware of the Great Matter of birth and death and the swiftness of impermanence. What are you doing sleeping when your eye of the Way is still clouded? If dullness and sinking arise repeatedly you should chant, "Habituality is deeply rooted and so I am wrapped in dullness. When will dullness disperse? May the compassion of the Buddhas and Ancestors lift this darkness and misery."
There was a master who sat with a heavy object on his head, which would fall with a crash whenever he started to doze ... and another who kept jabbing himself with a needle ... but I don't recommend that!
Also, brain wave studies have shown that Zazen may have some of the benefits of sleep, and may be a "sleep substitute" to some degree. Brain waves during Zazen are often in state otherwise found during sleep, or which are similar to brain waves in that peaceful place we encounter right before falling asleep while in bed ...
... which is also another reason that we can easily slip over the line into ZZZZZZZZzzzzzz.
Gassho, and Good Night, Jundo