What does Santiago admit about his motives for having killed the fish?
Santiago, the old man in The Old Man and the Sea, still takes pride in his ability as a fisherman, even after the eighty-four days without a catch, even after the ridicule from the other fishermen, even after Manolin's parents forbid the boy to fish with him because of his salao, his bad luck.
When Santiago goes out much farther than any of the others dare to go and catches the biggest fish anyone has ever seen, it confirms that he is still capable. He demonstrates that he can still match wits and strength with the creatures of the sea, that he can still make a living from the ocean as he always has done. Santiago regrets having had to kill it but takes pride in his landing of the fish, in spite of the difficulties and pain he experienced.
You did not kill the fish only to keep alive and to sell for food, he thought. You killed him for pride and because you are a fisherman. You loved him when he was alive and you loved him after. If you love him, it is not a sin to kill him.