John Keats' famous poem, "When I Have Fears," directly deals with knowledge of his impending death from tuberculosis (then called "consumption"). It was a very contagious disease, which not only killed John's mother and one of his brothers, but which would ultimately take his life before he turned thirty.

Knowledge that his health was poor, and probably aware that his life would be cut short, Keats pens this poem about all the things he will miss by dying young. It is something that everyone can identify with in the sense that everyone dies, and that there are always things we hope we can do, without the guarantee that we will have the opportunity to do so, but his death will come much too young, much too soon.

Keats knows that he will not have the opportunity to write all that is in his "teeming brain" because there is so much there and he has so little time...

When I have fears that I may cease to be 
Before my pen has glean'd my teeming brain...

...before he can read all the books piled next to him and enjoy the promise that each volume holds for him...

Before high-piled books, in charactery,
Hold like rich garners the full ripen'd grain...

Keats knows that he will gaze at the stars that promise romance, which can never be his...

When I behold, upon the night's starr'd face,
Huge cloudy symbols of a high romance,

And that opportunity will not be his to imagine what new realms might come to him through "the magic hand of chance"...

And think that I may never live to trace
Their shadows, with the magic hand of chance...

The time will come—when death takes him—when he will no longer be able to see the sweet face of a beautiful woman...

And when I feel, fair creature of an hour,
That I shall never look upon thee more...

...or fall in love and know the "faery" power of that love...

Never have relish in the faery power
Of unreflecting love;

...he knows that on the shore of the world, he will stand alone, as all people do at the doorstep of death, to think and wait until love and fame and all potential hopes and dreams sink into "nothingness"...

--then on the shore
Of the wide world I stand alone, and think
Till love and fame to nothingness do sink.

This poem is a sonnet (fourteen lines with a fixed rhyme scheme) written in iambic pentameter (ten syllables per line, with the stress on the second syllable/word in each of the five pairs). Often authors using this format will use the ninth line to shift the focus of the poem, and the sonnet's conclusion will be summarized in the rhyming couplet.

However, while Keats uses this form, he does not change the poem's focus at the ninth line: the message is very sad throughout the piece. The rhyming couplet does not indicate that he has resolved his fears.

He sees himself as exiled, cut off from all human endeavor and love, a lone figure on a forsaken shore, lost in thought. The inspired, feeling poet and lover has been diminished into a thinker, assaulted by fears that transform “Love,” “Fame,” and even self to “nothingness.”

He knows he will die, but he does not resign himself to it: he finds no comfort with the time he has left, or with the peace of religious thought, but sees himself pondering his end until all is gone—as he is gone.