take the bull by the horns

bullとは雄牛のことで、雄牛の角を掴む、というところから、


（問題、難題に）真正面に立ち向かう


という意味があります。

"Really?" He leaned back, fiddled with the controls on the armrest, pushed his seat back, and closed his eyes. The air around me grew cold, and I rubbed the goose bumps from my arms, turned again to the tiny rectangular window as the plane droned through cotton candy. Days earlier, when I'd told him Mami would never give me permission to go with him to Florida, Ulvi had said: "You must take the bull by the horns."I'd never heard that phrase, had no idea what it meant. He spoke less English than I did. Where did he pick it up? He didn't want me to run away with him. "Talk to her woman to woman," he'd said. "Explain the situation." But I couldn't face her, couldn't imagine the hurt in her eyes when I told her I'd had a choice, and I'd chosen him.
(Elmelardo Santiago. El hombre que yo amo. Ploughshares. 2000.)