Brutus is in conflict within himself. He loved Caesar, but he loved Rome more:
If there is anyone in this assembly, any dear friend of Caesar's, to
him I say that Brutus' love to Caesar was no less than his love. If
then that friend demands why Brutus rose against Caesar, this is
my answer,—Not that I loved Caesar less, but that I loved Rome
Clearly, Brutus is torn between his love for his friend and his love for his country. He is burdened with the fact that his friend Caesar had become overly ambitious. Knowing that his friend Caesar had changed, Brutus agrees to join the conspiracy against his good friend Caesar.
No doubt, Brutus is in utter turmoil. He must make a decision to kill his friend Caesar. Caesar has been a true friend to Brutus. Now, Brutus must betray his friend Caesar. He must bloody his hands with his friend Caesar's blood. Truly, Brutus is filled with conflict. He is in absolute distress. He cannot even share with his wife about the plan to murder Caesar.
While Brutus plans to kill Caesar, he surely did not expect the outcome to lead to his own downfall. Brutus did what he felt was the right thing. He killed Caesar because he had become overly ambitious. The struggle within Brutus is due to their friendship. Now, he must murder his friend to keep Rome safe.
Brutus expresses his anguish and turmoil over having had to kill his good friend:
As Caesar loved me, I
weep for him; as he was fortunate, I rejoice at it; as he was
valiant, I honor him; but, as he was ambitious, I killed him.
There are tears for his love; joy for his fortune; honor for his
valor, and death for his ambition.
No doubt, Brutus was in agony at his decision to kill his good friend Caesar, but it had to be done.