The night makes difficult a clear perception of surrounding things like that we have during the day.
Night is also felt as the time when we feel better our natural loneliness.
We might put these nocturnal facts together: since we lose the power of perception which links us with the world, we are forced to find ourselves without support and, therefore, in loneliness.
But the perception does not cease completely in the darkness. It is just weakened. And thus it leaves to be showed the relation between us and the world which is ignored while we perfectly perceive. For instance, we say „this thing is big, red, green, etc.” and we do not think at the correct form of speaking and thinking: „I perceive a thing which is different from me as being big, red, green, etc.”
The difference between us and the world is discovered at night through the feeling of loneliness. The anguish we feel is caused by such a difference, because the loneliness always speaks about our fearful relation to the world: we may lose ourselves into it and we may seem unimportant by comparing us with its greatness.