Existentialism - Sisyphus

While the story of Sisyphus is not new to me, this is the first time I have heard the full story. I found it quite interesting that he continued to avoid taking responsibility for his actions and paying the price for them, which of course led to his punishment, which most are familiar with...the whole pushing boulder up the mountain forever deal. My question is...while pushing the boulder up the mountain does seem pointless as it IS something that will continue to be done over and over for eternity and never ending, what does this struggle tell us about the human condition? What does it tell us about our search for meaning and purpose in life? Sisyphus, in my eyes, is likely pushing that boulder for pride. But why are we?