He who does not expect will not find out the unexpected, for it is trackless and unexplored.

He who does not expect the unexpected will not find it out. | The Art and Thought of Heraclitus: An Edition of the Fragments (1981) edited by Charles H. Kahn, p. 129 | He who does not expect the unexpected will not find it, since it is trackless and unexplored. | As quoted in Helen by Euripides, edited by William Allan (2008), p. 278 | Unless you expect the unexpected, you will not find it, for it is hidden and thickly tangled. | Rendering ἐὰν μή "unless" is more English-friendly without being inaccurate. As for the last clause, the point is that you can neither find it nor navigate your way through it. The alpha-privatives suggest using similar metaphoric adjectives to keep the Greek 'feel.' (S. N. Jenks, 2014)