In, "The Myth of Sisyphus" by Albert Camus there is the introductory idea that mankind is faced with inevitable consequences for the actions that they take. This can be related to the Existentialists idea of anguish. John-Paul Sartre argues that mankind is faced with the pressure of making ourselves responsible for our own actions and of others.
Camus introduces the character of Sisyphus as disobeying the higher powers for an apparent reason that is not clear, but it was enough for him to be sent to the underground world where he is faced with an eternal punishment.
Camu argues that Sisyphus counsciousness of his own pointless fate is what makes the myth tragic.
As Sisyphus retruns to push his rick everytime it falls introduces the idea of conciousness. Sisyphus accepts his reality and it may not be that he is optimistic about his punishment, rather he is aware that he has to live off a consequence.
Sisyphus may not be able to change the circumstances he is in or the meaningless universe he is living in but he is able to choose what his fate is. The trials of Sisyphus are very similar to the actions of human beings. Human beings are controlled and used to working 9-5 shifts and taking care of one another. Mankind is aware that we are all going to die one day, however, it is our freedom of choice to decide what we are going to do with ourselves between now and our death time.
Existentialism connects to Camus absurd universe because regardless of the acknowledgment it presents of the universe being meaningless it also revolves around the idea that we can create our own meaningful projects.