Yi Sun-sin wrote "Do not let my death be known" while literally dying. Ice cold.

Battle of Noryang, 1598. Final battle of the Imjin War. Yi Sun-sin takes a bullet. He's dying. Does he scream? Does he cry? No. He tells his son and nephew: "Do not let my death be known." Because if his troops found out their admiral was dead mid-battle, morale would collapse. So they kept beating the war drum as if nothing happened. The fleet won. The war ended. This man's last act on earth was a tactical decision. I genuinely cannot think of a harder way to go out.