What does μὴ ἐγκακεῖν mean in Luke 18:1?

What does μὴ ἐγκακεῖν mean in Luke 18:1? (Greek text from NA27) Note ἐγκακέω is the preposition ἔν combined with the verb κακέω. In BDAG “ἐγκακέω is defined as 1. become weary, tired w. ptc. foll. … 2. lose heart, despair …; be afraid, o…