How does Cassius's pessimism help to bring about his death? What lesson can be learned from this?

Cassius, ashamed that he has lived to see his best friend taken by the enemy, promises to give Pindarus his freedom in exchange for Pindarus ending Cassius’ life by stabbing him.

In this scene Cassius, perhaps the least noble of the main characters in he play, rises in stature. Here, however, he makes the one mistake that will prove fatal. His army is in retreat and on the verge of mutiny. They are surrounded by Antony, when Brutus’ troops, gaining the advantage over Octavius, stop fighting to loot the dead bodies instead of supporting Cassius’ army. When Pindarus, the slave Cassius captured years before in Parthia, announces, “Mark Antony is in your tents, my lord. / Fly therefore, noble Cassius, fly far off,” (Sc. 3, 10–11) the “noble” Cassius is determined to make his stand and not

retreat. When Cassius asks his friend Titinius to take his horse and ride down to see who is in his tents, Titinius indicates his love, honor, and respect for Cassius by his quick actions. He is ready and willing to put his own life on the line for his friend. “I will be here again even with a thought.” (Sc. 3, 20)

Cassius’ fatal error comes when he infers from Pindarus’ account that Titinius was captured by enemy troops. It is another example of how subjective interpretation effects the actions of another. True to his word, Cassius makes good on his pledge to Brutus to commit suicide rather than surrender. He calls on Pindarus to

return the kindness Cassius once showed him.