“Learn, that the present hour alone is man's.”
The Tragedy of Irene (1749), Act III, Sc. 2
Context: To-morrow's action! Can that hoary wisdom,
Borne down with years, still doat upon tomorrow!
That fatal mistress of the young, the lazy,
The coward, and the fool, condemn'd to lose
A useless life in waiting for to-morrow,
To gaze with longing eyes upon to-morrow,
Till interposing death destroys the prospect
Strange! that this general fraud from day to day
Should fill the world with wretches undetected.
The soldier, labouring through a winter's march,
Still sees to-morrow drest in robes of triumph;
Still to the lover's long-expecting arms
To-morrow brings the visionary bride.
But thou, too old to hear another cheat,
Learn, that the present hour alone is man's.
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Samuel Johnson 362
English writer 1709–1784Related quotes

As quoted in William the Silent (1897) by Frederic Harrison, p. 75
Context: It is not possible for me to bear alone such labours and the burden of such weighty cares as press on me from hour to hour, without one man at my side to help me. I have not a soul to aid me in all my anxieties and toils.

As quoted in A Book of French Quotations (1963) by Norbert Guterman, p. 365

Attributed to Plato in Confidence : How to Succeed at Being Yourself (1987) by Alan Loy McGinnis, this is probably a paraphrase of a statement which occurs in Letter of Advice to a Young Gentleman Leaving the University Concerning His Behaviour and Conversation in the World (1907) by Richard Lindgard: "Take heed of playing often or deep at Dice and Games of Chance, for that is more chargeable than the seven deadly sins; yet you may allow yourself a certain easie Sum to spend at Play, to gratifie Friends, and pass over the Winter Nights, and that will make you indifferent for the Event. If you would read a man’s Disposition, see him Game; you will then learn more of him in one hour, than in seven Years Conversation, and little Wagers will try him as soon as great Stakes, for then he is off his Guard."
Variants:
You can learn more about a person in an hour of play than in a year of conversation.
Attributed to Plato in Food Is the Frosting-Company Is the Cake (2007) by Maggie Marshall
You learn more about a person in an hour of play than in a year of conversation.
Attributed to Plato by former Alaska Gov. Sarah Palin, as quoted in "Aspiring philosopher Palin quotes 'Plato'" (9 July 2009) http://thinkprogress.org/2009/07/09/palin-plato/
Misattributed

“How important, therefore, to learn before leaving England to move man through God by prayer alone.”
(J. Hudson Taylor. A Retrospect. Philadelphia: China Inland Mission, n.d., 15).

“If there be only hours, at least learn what there is time to learn.”
Source: A Fire Upon the Deep (1992), Chapter 41 (p. 580).

“Enjoy the present smiling hour,
And put it out of Fortune's power.”
Quod adest memento
componere aequus.
Book III, ode xxix, line 32 (as translated by John Dryden)
Odes (c. 23 BC and 13 BC)