A great German philosopher, Arthur Schopenhauer (1788-1860) wrote in his famous "Will to Live":
Awakened to life out of the night of unconsciousness, the will finds itself an individual, all striving, suffering, erring; and as if through a troubled dream it hurries back to its old unconsciousness. Yet till then its desires are limitless, its claims unexhaustible, and every satisfied desire gives rise to a new one. No possible satisfaction in the world could suffice to still its longings, set a goal to its infinite cravings, and fill the bottomless abyss of its heart. Then let one consider what as a rule are the satisfactions of any kind that a man obtains. For the most part, nothing more than the bare maintenance of this existence itself, extorted day by day with unceasing trouble and constant care in the conflict with want, and with death in prospect. Everything in life shows that earthly happiness is destined to be frustrated or recognized as an illusion.
There is only one inborn error, and that is, that we exist in order to be happy. It is inborn in us because it is one with our existence itself, and our whole being is only a paraphrase of it, nay, our body is its monogram. We are nothing more than will to live and the successive satisfaction of all our volitions is what we think in the conception of happiness.
... Our life is like a payment which one recieves in nothing, but copper pence, and yet must then give a discharge for: the copper pence are the days; the discharge is death.
Jean-Paul Sartre (1905-1980), a great French philosopher and existentialist wrote similarly in "The Age of Reason",
I am my own taste, I exist. That is what existence means: draining one's own self dry without the sense of thirst.
... For nothing: this life had been given him for nothing, he was nothing and yet he would not change: he was as he was made. He yawned: he had finished the day, and he had also finished with his youth. Various tried and proved rules of conduct had already discreetly offered him their services: disillusioned epicureanism, smiling tolerance, resignation, flat seriousness, stoicism-- all the aids whereby a man may savor, minute by minute, like a connoisseur, the failure of a life. He took off his jacket and began to undo his necktie. He yawned again as he repeated to himself: "It is true, it is really true: I have obtained the age of reason."
Well, existentialism that was born and developed by writings of these philosophers and others, including Nietzsche, Kafka, Gasset was a product of nihilism, another trend in philosophy. Nihilism-- rejection and negation of everything, reduction of certain settled things into nothing. At the same time, existentialism raised the human being and sanctified its existence by postulating that there is nothing wrong with selfish and self-centered human 'existence'. That people have a right to live their lives to the utmost, to the most ridiculous fullness and richness... That narcissism and epicureanism were not that bad... Existentialism was also affected by voluntarism, another trend in philosophy, which promulgated the willpower as the basis of human life... It must be known that existentialism was a philosophy to counter Marxism. Since Marxism was focused on the 'community', not the individual, the existentialism felt that individualism was under an assail and thus needed support. Idealism and materialism of the 18th century philosophy were replaced by Marxism and existentilism in the late 19th and 20th centuries.
But of course, one of the necessary by-products of individualism was the lonely and depressed individual, stranded on the road all alone, and in despair. The communitarianism on the other hand provided the joyful 'community', a mass of people, at the expense of one individual's needs and wishes... Thence, the writings of all existentialists were filled with this longing for happiness and satisfaction of inner dreams... Perhaps, the only existentialist, who truly understood this was Soren Kierkegaard (see on this blog). He is considered the father of existentialism. Yet, he wrote in contrast with most who followed him,
The great thing, as I regard it, is to live in the congregation, to bring something finer out of it, if one is able; at all events to subordinate oneself to it and put up with it if one is unable to better it.