You live like this, sheltered, in a delicate world, and you think, no, you know you are living. 
Then you read a book, hear a song, take a trip… 
and you discover that you're not alive, you haven't been for a while, that you are hibernating. 
The symptoms of hibernating are quite easily detectable: 
first, restlessness. 
second, well
The second symptom (when hibernating becomes dangerous and might degenerate into death):
 The absence of pleasure. 
That is all.
 It appears like an innocuous illness. 
Monotony, boredom, death.
 Millions live like this (or die like this) without knowing it. 
They work in offices. 
They drive a car. 
They go out with their families. 
They raise children. 
And then some shock treatment takes place, a person, a book, a song, and it awakens them and saves them from death. 
Some never awaken.