why?

Santiago has not had much luck fishing. He is old and worn out. Still Santiago is hopeful,

But, he thought, I keep them [the fishing lines] with precision. Only I have no luck any more. But who knows? Maybe today. Every day is a new day. It is better to be lucky. But I would rather be exact. Then when luck comes you are ready.

Santiago sees everyday as a gamble. It can bring luck, it can bring nothing, it can bring sorrow. Like his idol the great Great DiMaggio, Santiago has slumps too. Santiago's believes that having luck is an important part of fishing.