Two generations after the Black Death, a book appeared in Europe which bore the title Ars Moriendi, "the Art of Dying." It is a manual intended both for the dying and those who visit and console them, and it is believed to have been written by a Dominican friar, likely in 1415. A later Ars Moriendi from ca. 1450 consists only of a series of eleven woodcuts illustrating what its compiler regards as the central portion of the longer work, which discusses five temptations which prevent a dying person from escaping their sins and advises on how to overcome them.
These books are, of course, part of a broader tradition of art, literature, and philosophy built around the theme of remembering one's own mortality. The memento mori tradition dates back to antiquity, when Roman generals marching in triumph would be followed by a slave whose task was to remind them that, although they are at the peak of their power and fame today, they are still mortal. In the years following the plague, however, it took on new popularity, and seems to have acquired a new and life-affirming message which makes such art no less relevant in the present day.
The Ars Moriendi volumes inspired an entire tradition of consolatory literature for the dying and those touched by their deaths, which is sometimes said to have petered out in the 17th century. In truth, it never ended, but merely transformed; over time, the emphasis shifted to the notion (present from the start) that the most important preparation for a good death is living a good life, until eventually the newer handbooks stopped being about death except as the capstone of a life well lived. Brief manuals on living well, whether derived from various specific philosophical and theological traditions or composed de novo from various short aphorisms meant to be relevant to modern life, continue to sell quite well today.
The popularity of the memento mori in the late Middle Ages, and the concurrent emergence of manuals on death, is perhaps no surprise. The Black Death is only the most famous of a series of lesser outbreaks of bubonic plague which followed it, and other sorts of epidemics were hardly uncommon; meanwhile, France was embroiled in the Hundred Years' War, and local wars were claiming lives everywhere else. It was an era when death could rarely be said to have come at what was regarded as its proper time.
It is a past, in other words, which may be much like our future. Today, medical science is steadily extending our notion of what is considered a "normal" human lifespan, and it's entirely possible we may someday reach a time when the idea of "dying of old age" is but a memory. But a long and full life means many more opportunities for an unexpected death along the way.
According to the broader tradition of Ars Moriendi literature, there is no such thing as dying well at the end of a life badly lived. This is defined entirely within the theological tradition from which these manuals originate, so that we are told of the need to imitate Christ in life; when death does arrive, the most important thing is said to be that the person release themself from their sins and accept divine grace. Those around them are instructed to ensure the room contains crucifixes and other reminders of salvation, and to ask them a series of questions which invite them to repent and to more fully accept Christ; those about to die are warned of five temptations which might stop them from achieving salvation, and are counseled on how to overcome them. The illustrations which comprise the shorter of the two fifteenth-century manuals focus entirely on these five temptations, consisting of an illustration of the Devil setting forth each one followed immediately by a depiction of its rejection; after these ten paired images we are shown a dying man's soul being taken up into Heaven while the Devil is left below to curse his failure.
Throughout this time, being constantly exposed to artistic reminders of death was normal. Many people chose to carry small ones on their persons. Death was seen as a thing to accept, not because it would come at its appointed time - for, as so many of the images make plain, there is no appropriate time, but death will come anyway. Rather, acceptance of death was mostly a simple matter of accepting that it was inevitable, and letting that knowledge spur one to living well. So, while these images look morbid to us today who so often shy away from consideration of death, to the late medieval mind they are a reminder to make the most of what time we have.
The changing shape of human mortality in these modern times is something our society has yet to decide how to react to, philosophically. And while I have not made up my own mind about the details of how I feel about it, I know this: I reject utterly the notion that the inevitability of death is somehow desirable. But I also refuse to let myself be so afraid of death that I shun all risk of its arrival, when so many of the things that put us in trivially greater danger are among those which make a long life worth living in the first place. While I'm young enough that my death would, by convention, be considered quite a shock if it came any time soon, I've already been hospitalized twice with potentially life-threatening conditions. Once, I needed surgery for something that simply happened by chance, and once I put myself at risk doing something I loved, and continued to do almost immediately on returning home. How am I to react to those experiences? How am I to react to the deaths of loved ones, and to friends' grief when their own loved ones pass on? These are not trivial questions, but the medieval answer is a good start - remember that you will die, and let that knowledge inspire you to live a great life while you have the chance.