What is the "Dark night of the soul"?

The following statement was found high in Google's search results on the subject -

"'The Dark Night of the Soul' is one of the most painful, isolating, and destabilizing experiences in life. Yet it is also a tremendous blessing in disguise."

Coupled with “that which does not kill us, makes us stronger”, attributed to Friedrich Nietzsche, and speaking from my own life experiences, this will lead you to your suicide but for remarkable fortitude, humility and action. Personally, I began classical piano playing from nothing at the age of 21, and I ultimately achieved a college level; but piano led to further diversification in my life, and more. My mother maintains the instrument saved my life.

This experience represents a total breakdown of everything that is us, at the most fundamental levels. It doesn't mean dissociation from our families or loss of a sense of gender. In a greater part though, identities and group affiliations, etc.: the things we don't need to hold so much store in, are especially vulnerable and likely to be lost. That's very painful, but vanities such as our physical attractiveness and unfounded confidence, may go too, perhaps with more pain. After all of this, we either rebuild and/or begin everything again, and in a better way, or rather a more robust way, i.e. a genuine way; or our life is over.

Having pointed out that I experienced such a misfortune, it shouldn't be a surprise to anyone, that my primary book: "I am", is strongly against us forming identities, accepting labels, and entering the mindset of groups.

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Most things involve shades of grey and are not about blacks and whites alone. It would be crass for me to suggest people attempt to achieve mitigations, just in case they have a "Dark night of the soul" !!! They are not so common. Instead, I think that we are stronger, less vulnerable, and more genuine, if we avoid these identities, labels, and anything else which removes our individuality.