Explain What Sartre Means When He Says, "Nor, on the Other

Explain what Sartre means when he says, "Nor, on the other hand, if God does not exist, are we provided with any values or commands that could legitimize our behavior. Thus we have neither behind us, nor before us in a luminous realm of values, any means of justification or excuse. We are left alone, without excuse. That is what I mean when I say that man is condemned to be free." Do you agree with Sartre? Explain your answer.