Alberto Moravia
"There are many reasons for keeping a diary: to make a note of facts that one considers important; to open one's heart, to give vent to one's feelings, to make confessions; from the instinct of economy which sometimes encourages a writer to make good use of even the smallest crumbs of his life, so that he may have one more book to publish; or again from vanity and self-satisfaction."

Source: The Lie, (London: Secker & Warburg, 1966. Tr. Angus Davidson). p. 7.