"For if there is a sin against life, it consists perhaps not so much in despairing of life as in hoping for another life and in eluding the implacable grandeur of this life"

Albert Camus is suggesting that it is a sin to wish for a life beyond this one, and to attempt to get away the truth of this life. He thinks that life is grand and must be embraced, not avoided. He is stating that it is incorrect to attempt to leave the difficulties of life, and to instead accept them and live life to the maximum. He is likewise suggesting that it is incorrect to put our faith in something that is not real, such as an afterlife, and rather to focus on today. He is encouraging us to accept life for what it is and to take advantage of it. He is warning us versus trying to get away the reality of life, and instead to embrace it and maximize it.