Another view
Patrick Forsyth links the sayings of others to the emphasis you might give your writing.
There is something about a good, pithy quotation that appeals to many people. It is the succinctness of such things that give them their appeal, the summing up of a broad thought in a very few words. While it does not do to overuse them, there are some kinds of writing in which the occasional quotation adds usefully: ‘I always have a quotation for everything – it saves original thinking’ – (Dorothy L Sayers).