ἀγωνίζεσθαι, ἐπιζητεῖν, εὑρίσκειν καί μή εἴκειν → to strive, to seek, to find, and not to yield (Tennyson, Ulysses)
obstinacy: P. αὐθάδεια, ἡ, Ar. and V. αὐθαδία, ἡ.
harshness: P. σκληρότης, ἡ.
firmness: P. καρτερία, ἡ.