How would you explain determination in an essay on The Old Man and the Sea?

Determination is definitely one of the key aspects of the
character of Santiago in this excellent novel, and can easily be demonstrated in terms
of its meaning through his perseverance and unyielding attitude in catching the big fish
that is his goal. A dictionary defines determination as "firmnness of purpose or
resolve," and we can definitely see this in the patient yet determined way that Santiago
fishes for his big catch--a fishing session that takes days and results in Santiago
having to use every ounce of his energy, knowledge and perseverance to see it through to
its conclusion. Note how, just before stabbing the fish with his harpoon, Santiago
himself acknowledges exactly what his determination has cost
him:

I am
tireder than I have every been, he thought, and now the trade wind is
rising.

Thus when we think of
determination in the novel it is hard not to associate it with Santiago and the way that
he carefully and painstakingly brings the fish in and manages to kill
it.