Fig.: to face up to a difficult or dangerous situation; to take action in a crisis

The situation was desperate, so I decided to take the bull by the horns and demand a raise in salary even though it might cost me my job and, guess what, I got it!

La situazione era disperata, così decisi di prendere il toro per le corna e chiesi un aumento di stipendio anche se poteva costarmi il posto e, pensa un po', l'ho ottenuto!

We can't go on like this: we must take the bull by the horns and settle this matter once and for all

Non possiamo andare avanti così: dobbiamo prendere il toro per le corna e sistemare questa faccenda una volta per tutte

In all probability this saying comes from the Spanish bullfighting. In the classic bullfight, the “banderillos” plant darts in the bull and then jump on his back and seize him by the horns to hold his nose down. In another version, it is the “matador” who tires the bull in various ways and then seize him by the horns in order to wrestle him to the ground