How to balance an attitude of "effortless non-striving" with proper posture? In Karma-Chagme's book, "A Spacious Path to Freedom", he emphasizes the importance of correct posture in directing the vital energies to the central channel.  In particular, he mentions (1) the tongue pressed against the pallet, (2) the teeth lightly touching, &amp; (3) gaze directed 4 finger lengths beyond the tip of the nose.    

I find that when I try to incorporate these three elements of posture into my practice I quickly store up tension in my jaw and throughout my face in general.  Additionally, keeping the gaze correctly placed is a full-time task that tends to excite the vital energies rather than relax the body.  

How can I balance keeping a correct posture while maintaining a relaxed attitude of effortless non-striving?
It would be possible for me to give a reply in the Theravada perspective hoping it might add value.


  (1) the tongue pressed against the pallet, 
  
  (2) the teeth lightly touching, 
  
  
    with clenched teeth and the tongue pressing on the palate
  


Vitakka Saṇṭhāna Sutta &amp; Maha Saccaka Sutta

Maha Saccaka Sutta further mentions:


  
    I thought thus, Aggi,vessana,
    
    ‘Suppose, with my teeth clenched and my tongue pressed against my palate, I beat down the mind with mind.’
    
    So, Aggi,vessana, I with my teeth clenched and my tongue pressed against my palate, I beat down the
    mind with mind.
    
    While I, Aggi,vessana, was subduing, restraining and beating down my mind, with teeth clenched and my tongue pressed against my palate, sweat poured from my armpits.
    
    Just like as a strong man, Aggi,vessana holding a weaker man by the head or by the shoulders, were to restrain, subdue, attack him, even so, when I, Aggi,vessana, with my teeth clenched, and my tongue pressed against my palate, sweat poured from my armpits.
    
    But although tireless energy was aroused in me, and undistracted mindfulness was established, my body was overstrained and ill at ease because I was exhausted by the painful striving.
    
    But such painful feeling that arose in me did not invade my mind and remain.
    
    I thought thus, Aggi,vessana, 
    
    ‘Suppose I practise the breathingless meditation.’
    So I stopped my in-breaths and out-breaths
    through my mouth and nose.
    
    While I did so, there was a loud sound of winds coming out from my ear-holes, just like a loud sound
    of winds from a smith’s bellows.
    
    Even so, Aggi,vessana, when I stopped my in-breaths and out-breaths, there was a loud sound of
    winds coming out from my ear-holes.
    
    But although tireless energy was aroused in me, and undistracted mindfulness was established, my
    body was overstrained and ill at ease because I was exhausted by the painful striving.
    
    But such painful feeling that arose in me did not invade my mind and remain.
    
    I thought thus, Aggi,vessana,
    
    ‘Suppose I practise further the breathingless meditation.’
    So I stopped my in-breaths and out-breaths through my mouth, nose and ears.
    
    While I did so, violent winds cut through my head, just as if a strong man were splitting my head open
    with a sharp sword.
    
    Even so, Aggi,vessana, when I stopped my in-breaths and out-breaths, there was a loud sound of
    winds coming out from my ear-holes.
    
    But although tireless energy was aroused in me, and undistracted mindfulness was established, my
    body was overstrained and ill at ease because I was exhausted by the painful striving.
    
    But such painful feeling that arose in me did not invade my mind and remain.
    
    I thought thus, Aggi,vessana,
    
    ‘Suppose I practise further the breathingless meditation.’
    So I stopped my in-breaths and out-breaths through my mouth, nose and ears.
    While I did so, there were violent pains in my head, just as if a strong man were tightening a
    tough leather strap around my head as a headband.
    
    Even so, Aggi,vessana, when I stopped my in-breaths and out-breaths, there were violent pains in my
    head.
    
    But although tireless energy was aroused in me, and undistracted mindfulness was established, my
    body was overstrained and ill at ease because I was exhausted by the painful striving.
    
    But such painful feeling that arose in me did not invade my mind and remain.
    
    I thought thus, Aggi,vessana,
    
    ‘Suppose I practise further the breathingless meditation.’ So I stopped
    my in-breaths and out-breaths through my mouth, nose and ears.
    
    While I did so, violent winds carved up my belly,
    just as if a skilled butcher or his apprentice were to
    carve up an ox’s belly with a sharp butcher’s knife.
    
    Even so, Aggi,vessana, when I stopped my in-breaths and out-breaths, violent winds carved up my
    belly.
    
    But although tireless energy was aroused in me, and undistracted mindfulness was established, my
    body was overstrained and ill at ease because I was exhausted by the painful striving.
    
    But such painful feeling that arose in me did not invade my mind and remain. 
    
    I thought thus, Aggi,vessana,
    
    ‘Suppose I practise further the breathingless meditation.’
    
    So I stopped my in-breaths and out-breaths through my mouth, nose and ears.
    
    While I did so, there was a violent burning in my body, just as if two men were to seize a weaker man
    by both arms, might set him on fire and roast him over a pit of burning coal.
    
    Even so, Aggi,vessana, when I stopped my in-breaths and out-breaths through my mouth, nose and
    ears, there was a violent burning in my body.
    
    But although tireless energy was aroused in me, and undistracted mindfulness was established, my
    body was overstrained and ill at ease because I was exhausted by the painful striving.
    
    But such painful feeling that arose in me did not invade my mind and remain.
  


This is method is used to subdue, restrain, attack the (bad) mind with the (good) mind or beat down the mind with mind. In a Theravada perspective this should be used as a last resort to get rid of distracting or unwholesome thoughts.

In a personal perspective I have found when Piti, a blissful feeling which might lead to bodily vibration, gets excessive it might help to resort to the above for a short duration. The rolled tongue seam to make a short circuit which might seem to defuse the vibrations. Even so you should just be mindful or arising and passing even in this state to effortlessly move to Passaddhi. (Ekā,dasaka) Cetanā’karaṇīya Sutta and (Dasaka) Cetanā’karaṇīya Sutta implies such transition of transcending Piti should be effortless or not forced.


  (3) gaze directed 4 finger lengths beyond the tip of the nose


The rationale is to:


Prevent you from getting sleepy
Develop a basic level of concentration


Perhaps as you become a more accomplished meditator you can drop this.


  
    Now, the eyes. Should we leave them open or should we close them? Many people believe that they must close their eyes that they cannot meditate with open eyes. If you are serious about what you are doing and have a sufficiently strong mind it is not difficult to practice with the eyes left open. Begin with the eyes open. Open them with the determination to gaze toward the tip of the nose. This is not at all impossible. It just takes a little effort to do so. Gaze at the tip of the nose so that the eyes will not get involved in other things. When we close our eyes we tend to be sleepy, so be careful about closing the eyes. Also, when the eyes are closed they become warm and dry. Mediating with the eyes open will help us to stay awake and will keep the eyes cool and comfortable. Further, this will help the mind to be concentrated; it will aid the development of samadhi. As samadhi (concentration) develops about half way, the eyes will close naturally by themselves. The eyelids will relax and drop shut on their own. There is nothing to worry about. The complete technique is to begin with the eyes open. Gaze at the nose tip until samadhi develops, then the eyes will close on their own. That takes care of the eyes. (46) 
    
    Practicing with the eyes open and gazing at the tip of the nose is automatically a noticeable level of concentration. If we establish all of the mind upon gazing at the tip of the nose, we will not see anything else. If we can do this, it will be a certain type of samadhi. We will profit from having this much concentration right from the start. Merely look at the nose without seeing anything else. If all of the mind, all of its interest, is set on looking at the nose, then nothing else will be seen. This samadhi is not insignificant. Therefore you ought to try to start with open eyes. (47) 
    
    Please observe that this is something anyone can do. We are intent upon gazing at the nose, at feeling the nose, and at the same time we feel the body breathing. Both can be done. It may seem that both are being done at exactly the same moment, but they are not. There is not anything unnatural or supernatural about it. Because of the mind’s great speed it is possible for the eyes to be gazing at the tip of the nose while being aware of breathing in and breathing out. You can see this for yourself. (48) 
  


Source: Anapanasati: Mindfulness of Breathing: Unveiling the Secrets of Life: a Manual for Serious Beginners by Ven Buddhadasa Bhikkhu or similar passage is found in Anapanasati: Mindfulness of Breathing by the same author


  I find that when I try to incorporate these three elements of posture into my practice I quickly store up tension in my jaw and throughout my face in general. Additionally, keeping the gaze correctly placed is a full-time task that tends to excite the vital energies rather than relax the body.


Above pratice perhaps can lead to stress and tension in the body, though vital energy will arise and mindfulness is established: "But although tireless energy was aroused in me, and undistracted mindfulness was established, my
body was overstrained and ill at ease because I was exhausted by the painful striving". You should be relaxed body and mind to get positive results in Buddhist meditation.


  How can I balance keeping a correct posture while maintaining a relaxed attitude of effortless non-striving?


You have to relax both body and mind. Tensions manifest as a tightness around the head or heart. Be mindful of the arising and passing of sensations in these areas. Your posture should be comfortable, relaxed and balanced, i.e., straight body. Also whatever posture you are in should be effortless, i.e., you should not be trying too hard to be in the posture. More on this see my other posts: How does one do mindfulness of breathing with relaxation?, Having trouble meditating long sessions (Physical pain), Losing awareness, what to do, when you can't meditate?, How does one calm one&#39;s bodily fabrications?

Also you the book you mentioned is the only guide practicing without a teacher may be dangerous in case you miss interpret and instruction or do not know how to handle complications. So you can try joining a formal course or finding a teacher. Some helpful site: http://dhamma.org, http://internationalmeditationcentre.org, World Buddist Directory