The message of existentialism, unlike that of many more obscure and academic philosophical movements, is about as simple as can be. It is that every one of us, as an individual, is responsible—responsible for what we do, responsible for who we are, responsible for the way we face and deal with the world, responsible, ultimately, for the way the world is.
It is, in a very short phrase, the philosophy of “no excuses!”
Life may be difficult; circumstances may be impossible. There may be obstacles, not the least of which is our own personalities, characters, emotions and limited means or intelligence.
But, nevertheless, we are responsible. We cannot shift the burden onto God, or nature, or the ways of the world. If nature made us one way, it is up to us to decide what we are to do with what nature gave us—whether to go along or fight back, to modify or transcend nature.