I've read a bit of Taoist philosophy over the last few years and was thrilled to see this thread. So I'm going to see if I contribute with a bit of Tao Te Ching, even though it's probably not quite as readily applicable as, say, Bruce Lee's or Miyamoto Musashi's meditations on mastering a specific skill. Tao Te Ching is shorter than the Book of Five Rings however, so I'll start here!
II: "... the sage keeps to the deed that consists in taking no action and practices the teaching that uses no words."
To me, it's interesting to see how different pixel artists try to instruct other pixel artists or influence the community as a whole. If one were to "take the role of the female", to use an expression from Tao Te Ching, then one would perhaps instruct by using no words in the sense of focusing only on one's own art and letting the art speak for itself. Teaching by reaching a certain ideal, as opposed to guiding others directly.
III: "Not to honour men of worth will keep the people from contention; not to value goods which are hard to come by will keep them from theft; not to display what is desirable will keep them from being unsettled of mind. Therefore in governing the people, the sage empties their minds but fills their bellies, weakens their wills but strengthens their bones. He always keeps them innocent of knowledge and free from desire, and ensures that the clever never dare to act."
Ref: the debate on trophies, ratings, rankings and awards on PixelJoint. Focus on improving your craft, not being honored by others. Be careful with complimenting those who win challenges, competitions, awards, etc, lest you contribute to their external motivation, making them more concerned with praise and recognition than the "tao of pixel art".
XI: "Thirty spokes share one hub. Adapt the nothing therein to the purpose in hand, and you will have the use of the cart. Knead clay in order to make a vessel. Adapt the nothing therein to the purpose in hand, and you will have the use of the vessel. Cut out doors and windows in order to make a room. adapt the nothing therein to the purpose in hand, and you will have the use of the room. Thus what we gain is Something, yet it is by virtue of Nothing that this can be put to use."http://en.wikipedia.org/wiki/Negative_space
XL: "Turning back is how the way moves; Weakness is the means the way employs."
Keep returning to your earlier projects to learn from old mistakes and see how you can improve. Be malleable, always ready to look at your past and present work with fresh eyes, open to suggestions and quick to discard what you've done so far, for the sake of learning something new.
XLVII: "Without stirring abroad, one can know the whole world; Without looking out of the window, one can see the way of heaven. The further one goes, the less one knows. Therefore the sage knows without having to stir, identifies without having to see (...)"
Don't go too far in your imitation of others, trust in your own artistic sense and develop your own style. (I don't know if this is useful to others, but I personally am more of a "reactive" artist - I tend to steal different ideas from various people and try to create new and interesting combinations, and I sometimes forget to "find my own voice" as it were)
LVI: "One who knows does not speak; one who speaks does not know."
Careful when giving advice to others.
LXIII: "Lay plans for the accomplishment of the difficult before it becomes difficult; make something big by starting with it when small. Difficult things in the world must needs have their beginnings in the easy; big things must needs have their beginnings in the small. Therefore it is because the sage never attempts to be great that he succeeds in becoming great."
Start out with the basics, ensuring the use of few colours, a good composition, correct proportions, etc. Make sure you have a good foundation before proceeding to add details and fancy effects, and you won't waste so much time.
LXVII: "The whole world says that my way is vast and resembles nothing. It is because it is vast that it resembles nothing. If it resembled anything, it would, long before now, have become small."
The principles of good pixel art can be applied to anything from simple gameboy sprites to vast, fullscreen landscapes and portraits. It can be applied to photorealistic pieces or entirely abstract art. Pixel art transcends style and function.
I really wanted to find a good Lao Tzu quote where I interpreted "the uncarved block" as the individual pixel, which cannot be "carved", but I failed to do so.