Know the value of time; snatch, seize, and enjoy every moment of it. No idleness, no laziness, no procrastination; never put off till tomorrow what you can do today.
Source: Letters to His Son, Philip Dormer Stanhope, 4th Earl of Chesterfield, letter of 26 December 1749 (published 1774)
Genuine Chesterfield, from the celebrated letter to his son on the use of time, dated 26 December 1749 Old Style and published in the 1774 collection 'Letters to His Son'. The original opens 'Know the true value of time' — the corpus text has dropped 'true'. Original punctuation is 'no procrastination: never put off till to-morrow what you can do to-day.' The 'never put off till tomorrow' proverb long predates Chesterfield and is not his coinage; he is quoting a commonplace inside a sentence that is his own.