“This could but have happened once,—
And we missed it, lost it forever.”

Source: Pride and Prejudice

1910s, At the Feet of the Master (1911)
Context: These are not my words; they are the words of the Master who taught me. Without Him I could have done nothing, but through His help I have set my feet upon the Path. You also desire to enter the same Path, so the words which He spoke to me will help you also, if you will obey them. It is not enough to say that they are true and beautiful; a man who wishes to succeed must do exactly what is said. To look at food and say that it is good will not satisfy a starving man; he must put forth his hand and eat. So to hear the Master's words is not enough, you must do what He says, attending to every word, taking every hint. If a hint is not taken, if a word is missed, it is lost forever; for He does not speak twice.
Four qualifications there are for this pathway:

Letter to Abigail Adams (17 July 1775)
1770s
Source: Letters of John Adams, Addressed to His Wife

Source: The Woman in Black

Have You Met Miss Jones?

Source: Poison

Source: Pride and Prejudice

"George Orwell, Artist" (1972), p. 46
The Good Word & Other Words (1978)