What were the tragic flaws of Cassius and Brutus in Act 5?

In Act V, Cassius's tragic flaw is that he too readily accepts defeat. When his servant, Pindarus, informs Cassius that "Mark Antony is in your tents, my lord Fly, therefore, noble Cassius, fly far off," Pindarus is mistaken. Mark Antony, Cassius's enemy, has not defeated Brutus, but Cassius too readily believes Antony has won and says, "My life is run his compass," meaning that his life has completed its circuit. He then bids his servant, Pindarus, to kill him and promises Pindarus his freedom if he does so. As he's dying, Cassius says, "Caesar, thou art revenged, Even with the sword that kill'd thee." In other words, Cassius believes his death is Caesar's revenge on him, as he asks Pindarus to kill him with the same sword that was used to kill Caesar.
Brutus, for his part, tempts fate by facing his opponents yet again, and this is his tragic flaw. After finding Cassius's dead body, Brutus urges on his troops, saying, "Romans, yet ere night We shall try fortune in a second fight." In other words, Brutus is "trying fortune" or testing fate by returning to the battlefield. In taking on Antony yet again, Brutus fails and is forced to retreat. Brutus then rushes upon his sword, held by his servant, Strato, and says, "Caesar, now be still: I kill'd not thee with half so good a will." In other words, Brutus is happier to die than he was to kill Caesar. Brutus's rushed return to the battlefield has resulted in his death.