Poor fool, what makes you promise yourself a long life, when there is not a day of it that goes by in security? Again and again, people who looked forward to a long life have been caught out over it, called away quite unexpectedly from this bodily existence. Nothing commoner than to be told, in the course of conversation, how such a man was stabbed, such a man was drowned; how one fell from a height and broke his neck, another never rose from table, another never finished his game of dice. Fire and sword, plague and murderous attack, it is always the same thing — death is the common end that awaits us all, and life can pass suddenly, like a shadow when the sun goes in.
 
[Ha stulte, quid cogitas te diu victurum, cum nullum diem habeas securum? Quam multi decepti sunt et insperati de corpore extracti! Quoties audisti a dicentibus, quia ille gladio cecidit, ille submersus est, ille ab alto ruens cervicem fregit, ille manducando obriguit, ille ludendo finem fecit, alius igne, alius ferro, alius peste, alius latrocinio interiit: et sic omnium finis mors est, et vita hominum tanquam umbra cito pertransit.]

Thomas à Kempis (c. 1380-1471) German-Dutch priest, author

The Imitation of Christ [De Imitatione Christi], Book 1, ch. 23, v. 7 (1.23.7) (c. 1418-27) [tr. Knox-Oakley (1959)]
    (Source)

(Source (Latin)). Alternate translations:

Thou art a fool, if thou think to live long, sith thou art not sure to live one day to the end. How many have been deceived through trust of long life, and suddenly have been taken out of this world or they had thought. How oft hast thou heard say that such a man was slain, and such a man was drowned, and such a man fell and broke his neck ? This man as he ate his meat was strangled, and this man as he played took his death ; one with fire, another with iron, another with sickness, and some by theft have suddenly perished ! And so the end of all men is death, for the life of man as a shadow suddenly fleeth and passeth away.
[tr. Whitford/Raynal (1530/1871)]

You are foolish if you think to live long, since you are not certain to live one day through to the end. How many have been deceived through trusting in a long life who have suddenly been taken out of the world much sooner than they had thought. How often have you heard that such a man was slain, and such a man was drowned, and such a man fell and broke his neck; this man choked on his food, and this man died in his recreation; one by fire, another by the sword, another by sickness, and some by theft have suddenly perished. And so the end of all men is death, and the life of man is as a shadow which suddenly glides and passes away.
[tr. Whitford/Gardiner (1530/1955)]

Ah foole, why dost thou think to live long, when thou canst not promise to thy selfe one day, how many have been deceived and suddenly snatcht away? How often dost thou hear these reports, such a man is slain, another is drowned, a third breaks his neck with a fall, this man died eating, and that man playing? One perished by fire, another by the sword, another of the plague, and another was slain by theeves, thus death is the end of all, and mans life passeth away like a shadow.
[tr. Page (1639), 1.23.29-31]

Does any Confidence of long Life encourage you to defer putting this good Advice in Execution speedily ? Nay, but reflect, fond Man, how little you can promise your self one poor single Day. How many Instances have you before your Eyes, or fresh in your Remembrance, of Persons miserably deluded and disappointed in this Hope, and hurried out of the Body without any warning at all? How often have you been surprized with the News of this Friend being run thro', another drowning crossing the Water, a Third breaking his Neck by a Fall, a Fourth fallen down dead at Table, or choaked with his Meat, a Fifth seized with an Apoplex at Play, a Sixth burnt in his Bed, a Seventh murthered, an Eighth killed by Thieves, a Ninth struck with Lightning, or Blasting, or Pestilence, a Tenth swallow'd up in an Earthquake. Such vast variety of Deaths surround us, and so fleeting a Shadow is the Life of a Man.
[tr. Stanhope (1696; 1706 ed.)]

Ah foolish man! why dost thou still flatter thyself with the expectation of a long life, when thou canst not be sure of a single day? How many unhappy fools, deluded by this hope, are in some unexpected moment separated from the body! How often dost thou hear, that one is slain, another is drowned, another by falling from a precipice has broken his neck, another is choaked in eating, another has dropt down dead in the exercise of some favorite diversion; and that thousands, indeed, are daily perishing by fire, by sword, by the plague, or by the violence of robbers! Thus is death common to every age; and man suddenly passeth away as a vision of the night.
[tr. Payne (1803), 1.23.8]

Ah! fool, why dost thou think to live long, when thou canst not promise to thyself one day. How many have been deceived and suddenly snatched away! How often dost thou hear these reports, Such a man is slain, another man is drowned, a third breaks his neck with a fall from some high place, this man died eating, and that man playing! One perished by fire, another by the sword, another of the plague, another was slain by thieves. Thus death is the end of all, and man's life suddenly passeth away like a shadow.
[ed. Parker (1841)]

Ah, foolish man! why dost thou think thou wilt live long, when thou canst not count upon a single day? How many souls, deluded by this hope, are, in some unexpected moment, separated from the body! How often dost thou hear, that "one is slain, another is drowned, another, by falling form a precipice, has broken his neck -- another is choaked in eating; another has dropt down dead in the exercise of some favourite diversion; and that thousands, indeed, are daily perishing by fire, by sword, by the plague, or by the violence of robbers! Thus, death is the end of all; and the life of man passeth away suddenly like a shadow.
[tr. Dibdin (1851)]

Ah, fool! why dost thou think to live long, when thou art not sure of one day? How many thinking to live long have been deceived, and snatched unexpectedly away? How often hast thou heard related, that such a one was slain by the sword; another drowned; another, from a height, broke his neck; one died eating, another playing? Some have perished by fire; some by the sword; some by pestilence; and some by robbers. And so death is the end of all; and man's life suddenly passeth away like a shadow.
[ed. Bagster (1860)]

Ah, foolish one! why thinkest thou that thou shalt live long, when thou art not sure of a single day? How many have been deceived, and suddenly have been snatched away from the body! How many times hast thou heard how one was slain by the sword, another was drowned, another falling from on high broke his neck, another died at the table, another whilst at play! One died by fire, another by the sword, another by the pestilence, another by the robber. Thus cometh death to all, and the life of men swiftly passeth away like a shadow.
[tr. Benham (1874)]

Ah! fool, why dost thou think to live long, when thou canst not promise to thyself one day. How many have been deceived and suddenly snatched away! How often dost thou hear these reports, Such a man is slain, another is drowned, a third has broken his neck with a fall, this man died eating, and that man playing! One perished by fire, another by the sword, another by the plague, another was slain by thieves. Thus death is the end of all, and man's life suddenly passeth away like a shadow.
[tr. Anon. (1901)]

Ah, foolish man, why do you plan to live long when you are not sure of living even a day? How many have been deceived and suddenly snatched away! How often have you heard of persons being killed by drownings, by fatal falls from high places, of persons dying at meals, at play, in fires, by the sword, in pestilence, or at the hands of robbers! Death is the end of everyone and the life of man quickly passes away like a shadow.
[tr. Croft/Bolton (1940)]

Ah fool, why think of living long when you have no certainty of a day? How many are mistaken and unexpectedly snatched away from the body. How often you have heard men say, he is killed by the sword, he is drowned, he broke his neck falling from a height, he choked while eating, he met his end while at play; one perished by fire, another from plague, another by a robber; and so death is the end of all; and man’s life passes suddenly like a shadow.
[tr. Daplyn (1952)]

Foolish man, how can you promise yourself a long life, when you are not certain of a single day? How many have deceived themselves in this way, and been snatched unexpectedly from life! You have often heard how this man was slain by the sword; another drowned; how another fell from a high place and broke his neck; how another died at table; how another met his end in play. One perishes by fire, another by the sword, another from disease, another at the hands of robbers. Death is the end of all men; and the life of man passes away suddenly as a shadow.
[tr. Sherley-Price (1952)]

You fool, why do you imagine you will live a long life. when you cannot be sure of a single day? Many have made this mistake and have been snatched away from life when they least expected it. So often you hear people saying that so and so has been killed in battle, and so and so drowned; another man has fallen from a height and broken his neck; one choked over a meal, another met his end in some sport. Others have died by -- fire, by violence, by sickness, by robbery -- death is the end of all, and the life of man passes by and vanishes like a shadow.
[tr. Knott (1962)]

Foolish one, why do you hope for long life when not even one day is certain? How many there are who think they will live long, but are mistaken and snatched from the body unexpectedly. How often have you heard it said: This man fell by the sword; that man was drowned; another fell and broke his neck; yet another was taken while at table and the other was at sport when the end came. One by fire, another by steel, yet another by pestilence and again another by thieves met his death. Death is the end of all men and man’s life is a shadow that quickly passes by.
[tr. Rooney (1979)]

Ah, my foolish friend! why do you think of living a long life when you are not sure of even one day? How many people are tricked and unexpectedly snatched away? How often have you heard it said that someone was murdered, someone else drowned, another broke his neck falling from a high place, yet another choked while eating, and someone else met his end while playing; one person died by fire, another from disease, and another was killed by a robber, and thus death is the end of all, and our life passes suddenly like a shadow.
[tr. Creasy (1989)]