“Poirot shook his forefinger so fiercely at me that I quailed before it. “Beware! Peril to the detective who says: ‘It is so small — it does not matter. It will not agree. I will forget it.’ That way lies confusion! Everything matters.””

Stebbing's Sir Walter Raleigh, chapter 30, gives these as Raleigh's words on being asked by the executioner which way he wanted to lay his head on the block.
Attributed

Sparks
The Note-Books of Samuel Butler (1912), Part XIV - Higgledy-Piggledy
Context: Everything matters more than we think it does, and, at the same time, nothing matters so much as we think it does. The merest spark may set all Europe in a blaze, but though all Europe be set in a blaze twenty times over, the world will wag itself right again.

Source: The Name of the Wind (2007), Chapter 14, “The Name of the Wind” (p. 113)

Quoted by William B. Whitman, The Quotable Politician p. 197.
Attributed
Source: By Any Means Necessary

Quoted by William B. Whitman, The Quotable Politician p. 197.
Attributed

As quoted in Sophie Scholl: The Real Story of the Woman who Defied Hitler (2009) by Frank McDonough
Context: I know that life is a doorway to eternity, and yet my heart so often gets lost in petty anxieties. It forgets the great way home that lies before it. Unprepared, given over to childish trivialities, it could be taken by surprise when the great hour comes and find that, for the sake of piffling pleasures, the one great joy has been missed. I am aware of this, but my heart is not. It seems unteachable; it continues its dreaming … always wavering between joy and depression.

'The weight of Atomes', in The Atomic Poems of Margaret (Lucas) Cavendish, Duchess of Newcastle, from her Poems, and Fancies, 1653, an electronic edition. Edited with an introduction by Leigh Tillman Partington. http://womenwriters.digitalscholarship.emory.edu/toc.php?id=atomic

Source: Prozac Nation