Why does Cassius say he is aweary of the world?

Cassius is tired of associating with people he cannot trust. He and Brutus fought, and Brutus accused him of being an angry, flawed man. After which, Cassius broke down and begged for death. He calls to his enemies (Antony and Octavian), "avenge yourselves alone on Cassius, for Cassius is aweary of this world, braved by his brother, checked like a bondman, all his faults observed."