From Viktor Frankl, Man's Search for Meaning

Any attempt at fighting the camp’s psychopathological influence on the prisoner by psychotherapeutic or psychohygienic methods had to aim at giving him inner strength by pointing out to him a future goal to which he could look forward.  Instinctively some of the prisoners attempted to find one on their own.  It is a peculiarity of man, says Frankl, that he can only live by looking to the future – sub specie aeternitatis.  And this is his salvation in the most difficult moments of his existence ....

The prisoner who had lost faith in the future – his future – was doomed.   With the loss of belief in the future, he also lost his spiritual hold; he let himself decline and became subject to mental and physical decay.  Usually this happened quite suddenly, in the form of a crisis, the symptoms of which were familiar to the experienced camp inmate.  We all feared this moment – not for ourselves, which would have been pointless, but for our friends.  Usually it began with the prisoner refusing one morning to get dressed and wash or go out on the parade grounds.  No entreaties, no blows, no threats had any effect.  He just lay there, hardly moving.  If this crisis was brought about by an illness, he refused to be taken to the sick-bay or to do anything to help himself.  He simply gave up.  There he remained, lying in his own excreta, and nothing bothered him any more....

[A]ny attempt to restore a man’s inner strength in the camp had first to succeed in showing him some future goal.  Nietzsche’s words: “He who has a why to live for can bear with almost any how,” could be the guiding motto for all psychotherapeutic and psychohygienic efforts regarding prisoners.  Whenever there was an opportunity for it, one had to give them a why – an aim – for their lives, in order to strengthen them to bear the terrible how of their existence.  Woe to him who saw no more sense in his life, no aim, no purpose, [no meaning] ... he was soon lost.