Today a man is here; tomorrow he is gone. And when he is out of sight, he is soon out of mind.

[Hodie homo est, et cras non comparet. Cum autem sublatus fuerit ab oculis, etiam cito transit a mente.]

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

The Imitation of Christ [De Imitatione Christi], Book 1, ch. 23, v. 1 (1.23.1) (c. 1418-27) [tr. Sherley-Price (1952)]
    (Source)

(Source (Latin)). Alternate translations:

For the common proverb is true: To-day a man , to-morrow none. And when thou art taken out of sight, thou art anon out of mind, and soon shalt thou be forgotten.
[tr. Whitford/Raynal (1530/1871)]

For the common proverb is true: Today a man; tomorrow none. When you are out of sight you are soon out of mind, and soon will be forgotten.
[tr. Whitford/Gardiner (1530/1955)]

To day a man, tomorrow none, and out of sight, out of mind.
[tr. Page (1639)]

To Day the Man is vigorous, and gay, and flourishing, and to Morrow he is cut down, withered and gone. A very little time carries him out of our Sight, and a very little more out of our Remembrance.
[tr. Stanhope (1696; 1706 ed.)]

To-day man is, and to-morrow he is not seen; And when he is once removed from the fight of others, he soon passeth from their remembrance.
[tr. Payne (1803)]

To-day the man is here; to-morrow he hath disappeared. And when he is out of sight, quickly also is he out of mind.
[ed. Parker (1841)]

Man is here to-day, and gone to-morrow: and when once removed from sight, soon perishes from remembrance.
[tr. Dibdin (1851)]

A man is here to-day, and to-morrow he is no longer seen. And when he is taken away from the sight, he is also quickly out of mind.
[ed. Bagster (1860)]

To-day man is, and to-morrow he will be seen no more. And being removed out of sight, quickly also he is out of mind.
[tr. Benham (1874)]

To-day we are here, to-morrow we disappear, and when we are gone, quickly also we are out of mind.
[tr. Anon. (1901)]

Today we live; tomorrow we die and are quickly forgotten.
[tr. Croft/Bolton (1940)]

Today man is; and tomorrow he has vanished. But when he is taken out of sight he also soon passes out of mind.
[tr. Daplyn (1952)]

Here man is today; tomorrow, he is lost to view; and once a man is out of sight, it's not long before he passes out of mind.
[tr. Knox-Oakley (1959)]

A man is here today and gone tomorrow, and once he is out of our sight it is not long before he is out of our minds as well.
[tr. Knott (1962)]

Today a man is and tomorrow he is gone. When he has been removed from our sight he is soon out of mind as well.
[tr. Rooney (1979)]

Today we are, and tomorrow we are gone. And when we are taken out of sight, we soon pass out of mind.
[tr. Creasy (1989)]