烈马 has a strong romantic-classical flavor — picture a Tang or Song general charging on a
千里马 (thousand-li horse). It anchors the proverb
好马配好鞍 (a good horse deserves a good saddle) and pairs with the verb
驯 (xún) 'to tame'. As a metaphor for a stubborn person it's almost always positive — strong-willed, not difficult.
