Let’s say, God/Self/Soul/Spirit is in the deepest depth of the unconscious (also said by Carl Jung).
Now, the libido/interest of the self usually resides both in the conscious and unconscious.
What happens in the dark night depression is basically a soul retrieval where, the libido is brought back to God which is in the deepest depths of the unconscious.
As the libido withdraws itself from the consciousness screen, your interests start to decline.
When almost the entire libido has withdrawn from consciousness, there is 0 interest in the ‘Entire consciousness screen’.
So in such a case, you are not interested in ANYTHING and also lose all will to live, because the entirety of the libido has moved to the unconscious.
All you have now in your consciousness is various manifestations/things of god, but 0 interest and possibly even a distaste.
There is incredible despair and all you want is to die/completely change/completely transform. But you dont see any way of that happening. So you just surrender to the mystery because with the loss of all hope, there is nothing to do but surrender. This drives the libido into intense contemplation and there is a cloud of unknowing across your entire consciousness screen because of withdrawal of interest which creates the dark night.
Eventually, the libido reaches the self(depth of unconscious), the experience of everything fundamentally changes, illumination happens and you are transformed.