Brutus last words indicate that he is still grieving over having had to kill Caesar:
Goodbye, good Strato.
—Now Caesar, be still.
I didn’t kill you with half so good a will.
Brutus is saying that it is easier to run on his own sword than to have had to kill Caesar. Brutus realizes that the enemy has defeated him. Rather than become Antony's prisoner, Brutus would rather die. He runs on his own sword. His last words indicate that he is still upset by having had to kill Caesar. He is stating that he is more willing to kill himself than to kill Caesar. Brutus never wanted anything but peace for all of Rome. He runs on his own sword and finally finds peace.
When Antony finds Brutus' dead body, he proclaims Brutus as the most honorable of all the conspirators:
This was the noblest Roman of them all.
All the conspirators, except him,
Did that they did out of jealousy of great Caesar;
Only he, in a general-honest thought
And common good to all, made one of them.
His life was gentle, and the elements
So mixed in him that Nature might stand up
And say to all the world, "This was a man!"
Antony praises him one last time.