We were two of a kind, and our relationship would endure as long as we did: but it could not make up entirely for the fleeting riches to be had from encounters with different people.
Source, in full
On her relationship with Jean-Paul Sartre, as quoted in "Did Simone de Beauvoir's open 'marriage' make her happy?" by Lisa Appignanesi, in The Guardian (9 June 2005) and her book Simone de Beauvoir (2005), p. 36, ISBN 1904950094