Michael Fishbane describes metanoia beautifully and precisely:

…But then it may happen that the thoughtless ordinariness of daily life is jolted and gives way to a more elemental specificity. Suddenly something occurs that claims us with an overwhelming intensity, and floods our sensibilities without any accompanying thoughts of its human meaning. Rather, the sense of rupture is all, and it seems as if primordial energies have burst from the depths and ripped the veil normally stretched over things, concealing them in blandness. Such moments may occur within the bounds of nature, as with the uprush of some overwhelming vista or sound; they may happen in the human world, as with the unsettling impact of sudden death or love; or they may happen through the creations of culture, as with the capacity of certain compositions to propel us to the edge of sensibility. We then shudder before what is given to us from the fullness of phenomenal existence, manifesting mysteries of the surge of things at the core of world-being. Just here is an absolute “somethingness,” pulsing in elemental specificity—for we suddenly sense the raw plenitude of existence; but here too, simultaneously, it seems, is a revelation of primordial “nothingness,” yawning like an “inconceivable chasm of invulnerable silence in which cataclysms of galaxies rave mute as amber”—for we also sense that the event is in excess of human meaning. In time we come back to our normal selves, and when we do we more knowingly confirm this happening and ourselves as well, answering the ever-present question “Where are you?” with the confession “Here I am—just here.” On such occasions, consequent to the restabilization of consciousness, a renewed subjectivity is aroused in us (the “here I am”), together with an awakened sense of the great immensity in which we are suffused, now experienced at a particular time and place (the “just here”).

These experiences may fundamentally change our lives; for though the primal depths may close over, and we return to more regular experiences of the world, the “sense of depth” may remain in mind. And if so, one is infused by an awareness of a twofold dimension to reality—the pervasive superflux of existence that underlies our lives, and its more delimited nature on the existential surface of things. Along with this dual sensibility may come an awareness of our role in circumscribing the boundless and naming what exceeds all terms. This hyperconsciousness need not put us at odds with things, for we are also natural beings, and adapting ourselves to the world of nature is part of our acculturated naturalness. But by becoming aware of this matter, we realize that the world is not just there as “a world,” fixed and final (like some substantial datum waiting to be disclosed), but is rather a happening, ever coming into actuality through human inventiveness; and that the self, for its part, is not just “a self,” fixed in nature and proclivity, but a self-consciousness, ever attuned to itself and its worldly involvements. In this way the eruptive, caesural event is kept in mind by a new attentiveness to the contingency of experience, and an attunement to the deeper nature of worldly existence. As this double dimension of existence is infixed in consciousness (as a bimodal mentalité ), our subjectivity and life-world are transformed.

It is the particular poignancy of the caesural moment that changes us and may induce a new mindfulness. For though the initial experiences silenced human expression, the sense of being overwhelmed by the event may give way to a sense of being claimed by it in a fundamental way. It is just that more conceptual (or self-conscious) sensibility which marks the moment with axial significance and calls the person to change their life. This is therefore not only a cognitive insight, through the perception of primordial forces underlying experience; it also carries a value component, through an awakening to the contingency of existence and the command to respond. When the precipitating moment is an elemental event of nature, such as an earthquake or flood, or the cycles of birth and death, and even when the occasion is a historical fact, such as some monstrous evil of deed or neglect, the charged moment palpably calls to our elemental nature and conscience, directing us to: Remember, Do Something, or Have Sympathy; and to the extent that one can fix these revelations in one’s mind through rituals of action and recollection, their moral charge remains, and the claim is continuous and does not fade. How we collect such events in our personal lives, and how we keep them alive, determines the nature of our character; and how a culture does this through education and the selection of events for public recollection affects the moral shape of society.