The first idea that came to me is that one must accept self imposed limitations for the sake of stability. There is a fine line between inspiration and insanity, and a certain stability is required so that one can survive long enough to perfect one's arts and/or one's progeny. There are many other ideas encoded here as well, that's just my first impression. Now I will go thru the poem in detail and see what else comes to mind.
The sea without lees is the ocean of the infinite, where the gods dwell, and Hermes is the messenger of the gods, the angel of inspiration. It is the ocean of transformation, symbolized also by the element mercury, the only metal liquid at common temperatures. Hermes, also known as Mercury, is pictured with wings on his head and feet, symbolizing that thought and inspiration are birdlike in their swiftness and their ability to go wherever they wish, over trackless places and barricades, "as the crow flies". Yet a bird whose feathers grow "variable", some much longer than others, would be unstable in his flight, just like there is a fine line between inspiration and insanity. This is why Icarus fell into the sea. So the bird of Hermes eats his feathers to keep them trimmed and shapely so that he can fly in a stable manner.
Sometimes he eats too much of his wings, just as the inspired person can go too deeply into their arts and consume themselves, and then his feathers are gone and he is still as a stone. Even so, the life force remains, and the bare bones of inspiration can quicken the "death" of a stagnant life path, if one but sits still thru the white and the red, that is, the completion of the cycles. Life and death are both parts of the same cycle. There are parts of our bodies which are dead (hair, the outer layer of teeth and skin, etc) and also a dead body teems with life, or at least it would if it were not embalmed. The last few lines of this poem acknowledge this and thank the gods for this sight or knowledge.
There is more to it than this, these are just a few impressions I got from the quote after thinking it over some. Since this quote speaks to you so powerfully, perhaps Hermes or Hermes' Bird is calling you to contemplate it for a while and devine all of its meanings, the most profound of which cannot be put into words.