An Overly Brief Introduction to Existentialism

By and large Existentialists believe that life is very difficult and that it doesn't have an "objective" or universally known value, but that the individual must create value by affirming it and living it, not by talking about it.

http://www2.webster.edu/~corbetre/philosophy/existentialism/whatis.html

In simpler terms, existentialism is a philosophy concerned with finding self and the meaning of life through free will, choice, and personal responsibility. The belief is that people are searching to find out who and what they are throughout life as they make choices based on their experiences, beliefs, and outlook. And personal choices become unique without the necessity of an objective form of truth. An existentialist believes that a person should be forced to choose and be responsible without the help of laws, ethnic rules, or traditions.

http://www.allaboutphilosophy.org/existentialism.htm

Quotations about Existentialist Thought

“Man is nothing else but what he makes of himself.”

― Jean-Paul Sartre, Existentialism and Human Emotions

“Au milieu de l'hiver, j'ai découvert en moi un invincible été.”

(“In the middle of winter, I have discovered within myself an invincible summer.”)

― Albert Camus

“Try again. Fail again. Fail better.”

― Samuel Beckett

“On the whole, men are more good than bad; that, however, isn't the real point. But they are more or less ignorant, and it is this that we call vice or virtue; the most incorrigible vice being that of an ignorance that fancies it knows everything and therefore claims for itself the right to kill. The soul of the murderer is blind; and there can be no true goodness nor true love without the utmost clear- sightedness.” ― Albert Camus

“There can be no question of holding forth on ethics. I have seen people behave badly with great morality and I note every day that integrity has no need of rules”

― Albert Camus, The Myth of Sisyphus and Other Essays

“Youth ends when egotism does; maturity begins when one lives for others.”

― Hermann Hesse, Gertrude

“We only have one life to live, and must go on with it to the end, that if we feel it is meaningless, then we ourselves must give it meaning.”

― Susan Moody, Return to the Secret Garden