Why is being optimistic beneficial?

Julius caesar. [brutus.] with this, she fell distraught, and, her attendants absent, swallowed fire. cassius. and died so? brutus. even so. cassius. o ye immortal gods! [enter lucius, with wine and taper] brutus. speak no more of her. give me a bowl of wine. in this i bury all unkindness, cassius. cassius. my heart is thirsty for that noble pledge. fill, lucius, till the wine o'erswell the cup; i cannot drink too much of brutus' love. [exit lucius. enter titinius, with messala] brutus. come in, titinius; welcome, good messala. now sit we close about this taper here, and call in question our necessities. cassius. portia, art thou gone? brutus. no more, i pray you. what moral dilemma does brutus confront in this excerpt? brutus lets go of his anger toward cassius and forgives him. brutus decides that he will not mourn portia and will stay loyal to cassius. brutus decides that he is too angry at cassius to remain friends with him. brutus questions whether cassius's life should be ended.