The first thing you need to do is settle on a story for your essay. There are obviously lots of things to choose from but it needs to be something you have read or watched. If you have absolutely no ideas, Nicholas Sparks (any of his books or his movies) almost always includes a love story and a death story. I would think that many could satisfy the requirements of this essay.
As far as filling your three paragraphs goes, you could follow this basic organization plan:
Paragraph 1: write a brief summary of the story. Be sure to include details about the hero, how he comes close to happiness, and how/why/when he dies.
Paragraph 2: Analyze why he did not experience full happiness before he died. What was left unfinished as a result of his death?
Paragraph 3: What were your personal feelings at the end of the story? Do you think he got what he deserved or do you pity him, and why?