Every artist knows how far from any real feeling of letting himself go his "most natural" state is--the free ordering, placing, disposing, giving form in the moment of "inspiration"--and how strictly and subtly he obeys thousandfold laws precisely then, laws that precisely on account of their hardness and determination defy all formulation through concepts (even the firmest concept is, compared with them, not free of fluctuation, multiplicity, and ambiguity).
What is essential "in heaven and on earth" seems to be, to say it once more, that there should be obedience over a long period of time and in a single direction: given that, something always develops, and has developed, for whose sake it is worth while to live on earth; for example, virtue, art, music, dance, reason, spirituality--something transfiguring, subtle, mad, and divine.
Friedrich Nietzsche, Beyond Good and Evil, Part V, section 188, Kaufmann, tr. Vintage (New York: 1966), pp. 100-101. As he calls it earlier in the passage, it is a 'long compulsion', and to understand what is inestimably valuable in, say, Stoicism, you should look for that in it which can be compared to something like the compulsion of meter and rhyme on language, which educates and strengthens and makes more alive the very words we use.