I think it is hard not to read this book and see the themes that it contains as an obvious comment on the life of Hemmingway and his experiences. Note that this is one of the last pieces of fiction that he wrote before his declining health and depression and eventually his suicide, and it certainly invites great analysis about the human condition and what it is to be a success. This story points towards the human struggle to achieve our dreams and what a bitter struggle that can sometimes be, as we can end up destroying those dreams that have driven us so strongly. Yet, at the same time, the novel stresses the importance of having dreams to aim for, even in our darkest and lowest moments, because without dreams, the novel suggests, we are not truly human. Thus it is highly significant that Santiago, even after he returns to his hut, still "dreams of the lions" in Africa, representing that his spark of humanity has not been extinguished by his momentous experiences.
Thus we can see this novel as a kind of allegory about Hemmingway and his life and work, and how even in the midst of the dark times that he suffered, he was able to maintain some form of hope until his declining health caused him to commit suicide. In addition, we know that Hemmingway was a great fisherman, and so a lot of his personal experience helped to create the authenticity of this novel.
Lastly, we can also look at the theme of old age and how it is presented. Hemmingway wrote this in his sixties, and Santiago in the novel at various stages looks back upon his life and his former strength and what he was able to do when he was young. In spite of Santiago's obvious recognition of how age has impacted him, he is still able to plan another fishing expedition and carry on with the struggle of living.