Perseverance, defined by Merriam-Webster as "continued effort to do or achieve something despite difficulties, failure, or opposition," is one of the defining traits of Santiago, the main character of Hemingway's The Old Man and the Sea. We see this from the very beginning of the book when we are informed that Santiago has gone 84 days now without catching a fish—but he is determined to go out and try again anyway, even without the help of his apprentice.
In its essence, this is a "man versus nature" story; Santiago is isolated on his boat, fighting against the willful, powerful marlin fish he has caught and the tempestuous ocean for almost the entirety of the short novel. The marlin may be hooked on the end of Santiago's line, but it is stronger than the man's small skiff, and instead of being pulled back to shore, the marlin pulls the boat farther out into the water. Santiago can do nothing but hold on, which he does for two whole days, until his hands are injured. In the face of his hurt palms, all Santiago has to say is, “And pain does not matter to a man.” The strength of Santiago's desire to achieve his goal and break his streak of bad luck makes even pain irrelevant to him. He carries on regardless, determined in his task—the very definition of perseverance.