"Existence is prior to essence. Man is nothing at birth and throughout his life he is no more than the sum of his past commitments. To believe in anything outside his own will is to be guilty of 'bad Faith.' Existentialist despair and anguish is the acknowledgement that man is condemned to freedom. There is no God, so man must rely upon his own fallible will and moral insight. He cannot escape choosing." (Chambers.)
The philosophy of existentialism depicts man, alone and afraid in a world he never made. Existentialism rejects abstract theoretical systems such as the one espoused by Hegel; it emphasizes the supreme importance of the individual and his choices. (Nietzsche was an existentialist.) This philosophical movement has had more of a following in mainland Europe (especially Germany and France) than in English-speaking countries. The most famous of the French existentialists was, of course, Jean-Paul Sartre. Sartre's WW II experience is an example of what existentialists see as the ever-present necessity for individual choice. His was a very obvious case in point, a choice which all Frenchmen faced at the time: collaboration, resistance, or quiet self-preservation.

"There is no ultimate meaning or purpose inherent in human life; in this sense life is 'absurd'. We are 'forlorn', 'abandoned' in the world to look after ourselves completely. Sartre insists that the only foundation for values is human freedom, and that there can be no external or objective justification for the values anyone chooses to adopt.1
To Sartre human life is an "unhappy consciousness," a "useless passion." To this, I am obliged to comment: I believe that one's life is, in itself, a value; and the objective standard for one to follow is that which advances this value. Holding one's own life as the ultimate value, a person can see the importance of the right choices among the many, choices which it is hoped will lead to the protection and advancement of an individual's greatest value, that individual's own life.
Outside of Sartre's view that life is an "unhappy consciousness," a "useless passion," much of what Sartre asserts makes sense and counters the dangerous notions of Freud and his ilk. For instance, Sartre emphatically rejects the idea advanced by Freud that certain mental events have unconscious causes. Emotions, he says, are not outside the control of our wills, if one is sad it is because one chooses to be sad; we are responsible for our emotions; we are, ultimately, responsible for our own behaviour. According to Sartre, man is free and being conscious of this fact, can bring on pain, or anguish; and typically we try to avoid the consciousness of our own freedom.

"The crucial concept in his diagnosis is that of self-deception or 'bad faith' (mauvaise foi). Bad faith is the attempt to escape anguish by pretending to ourselves that we are not free. We try to convince ourselves that our attitudes and actions are determined by our character, our situation, our role in life, or anything other than ourselves. Sartre gives two famous examples of bad faith. He pictures a girl sitting with a man who she knows very well would like to seduce her. But when he takes her hand, she tries to avoid the painful necessity of a decision to accept or reject him, by pretending not to notice, leaving her hand in his as if she were not aware of it. She pretends to herself that she is a passive object, a thing, rather than what she really is, a conscious being who is free. The second illustration of the cafe waiter who is doing his job just a little too keenly; he is obviously 'acting the part'. If there is bad faith here, it is that he is trying to identify himself completely with the role of waiter, to pretend that this particular role determines his every action and attitude. Whereas the truth is that he has chosen to take on the job, and is free to give it up at any time. He is not essentially a waiter, for no man is essentially anything."2