Sartre said it best: existence precedes essence. We are not born with a purpose, we create one.
Camus described the clash between our hunger for meaning and a silent universe. His conclusion was not despair but defiance: we must imagine Sisyphus happy.
If nothing is predetermined, every choice is ours, and so is the responsibility. Sartre called trying to escape this bad faith, hiding behind roles like "I'm just doing my job".
It is a surprisingly hopeful philosophy for something that begins with "life has no inherent meaning".