It is perhaps in his very suffering that the old man gains so much of his value. According to his outward appearance and condition, he is an absolutely waste, unlucky, and some what destitute old man hanging onto an absurd idea of being successful again someday. He hasn't caught a fish in nearly three months and barely scrapes together and borrows enough money to buy bait fish.
In his incredible battle with the noble fish and the hunger and thirst and horrible sunburn and pain that he feels during his fight, he demonstrates his nobility, his ingenuity, his resourcefulness, and his incredible resolve while dealing with all of these discomforts and never once giving up. Even when there is nothing left of the fish but some bones, he still manages to keep himself alive long enough to return home and think again of returning to the sea another time.