I am thus responsible for myself and for all men, and I am creating a certain image of man as I would have him to be. In fashioning myself I fashion man.
Man is nothing else but what he purposes, he exists only in so far as he realises himself, he is therefore nothing else but the sum of his actions, nothing else but what his life is.
In reality and for the existentialist, there is no love apart from the deeds of love; no potentiality of love other than that which is manifested in loving; there is no genius other than that which is expressed in works of art.
In life, a man commits himself, draws his own portrait and there is nothing but that portrait. No doubt this thought may seem comfortless to one who has not made a success of his life. On the other hand, it puts everyone in a position to understand that reality alone is reliable; that dreams, expectations and hopes serve to define a man only as deceptive dreams, abortive hopes, expectations unfulfilled; that is to say, they define him negatively, not positively.
:- Above are all by Sartre
For the existentialists engagement is the source of meaning and value; in choosing myself I in a certain sense make my world.
:- Essay on Existentialism in the Stanford Encyclopedia of Psychology