“The difference between the almost right word and the right word is really a large matter - it's the difference between the lightning bug and the lightning.”
The great enemy of clear language is insincerity. When there is a gap between one's real and one's declared aims, one turns as it were instinctively to long words and exhausted idioms, like a cuttlefish spurting out ink.
George Orwell, "Politics and the English Language," 1946
Write with nouns and verbs, not with adjectives and adverbs. The adjective hasn't been built that can pull a weak or inaccurate noun out of a tight place.
William Strunk and E.B. White, The Elements of Style, 1959
(A variation of this idea: "The road to hell is paved with adverbs." - Stephen King, On Writing: A Memoir of the Craft, 2000.)