Tranquillity ~ calmness, serenity

"Poetry is the spontaneous overflow of powerful feelings: it takes its origin from emotion recollected in tranquillity."
~ Wm. Wordsworth (1770 - 1850) English poet.

"Sorrow is tranquillity remembered in emotion."
~ Dorothy Parker (1893 - 1967) American critic, humorist.

"There ought to be moments of tranquillity in great works, as in life after the experience of passions, but not moments of disgust."
~ Voltaire (1694 - 1778) French writer, philosopher.

Source: Oxford Dictionary of Quotations, Oxford University Press, 2001.