The Roman Emperor Vespasian was making tough and consequential decisions while being terminally ill in his bed. When his physician told him that it was negatively affecting his health, he said: “An emperor must die standing.”
Montaigne writes about this in his essay Against Laziness and gives more examples of a man’s ability to selflessly concentrate on necessary tasks (usually concerning others) while knowing that death is near.
Cato the Younger, a major enemy of Julius Caesar, on the day when he decided to commit suicide, didn’t do anything exceptional: he calmly had his meal, read a book, and went to sleep. Alexander the Great, before his famous battle of Gaugamela against Darius III, with the odds of 1 against 2 in an open battlefield, had a sleep so deep that his generals struggled to wake him up.
There can be found more examples, and different people will interpret them in different ways. My conclusion is this: These men were doing what was necessary while not concerning themselves with the outcome of fate.
Update: I read Suetonius recently (April 28, 2023). The Life of Otho shocked me. Did Montaigne read Suetonius when writing his essay on not judging happiness until death? Well, Suetonius himself attributes the phrase “an emperor must die standing” to Vespasian in The Life of Vespasian! If I remember correctly, the demise of Brutus also had something great to it. Are there any recent examples of a great death or it already is the legacy of the past?