Here's one of the most heart breaking love letters ever written:
Wednesday Morning. Kentish Town, 1820
My Dearest Girl,
I have been awake this morning with a book in my hand, but as usual I have been occupied with nothing but you: I wish I could say in an agreeable manner. I am tormented day and night. They talk of my going to Italy. 'Tis certain I shall never recover if I am to be so long separate from you: yet with all this devotion to you I cannot persuade myself into any confidence of you. Past experience connected with the fact of my long separation from you gives me agonies which are scarcely to be talked of. When your mother comes I shall be very sudden and expert in asking her whether you have been to Mrs. Dilke's, for she might say no to make me easy. I am literally worn to death, which seems my only recourse. I cannot forget what has pass'd. What? nothing : with a man of the world, but to me deathful. I will get rid of this as much as possible. When you were in the habit of flirting with Brown you would have left off, could your own heart have felt one half of one pang mine did. Brown is a good sort of Man - he did not know he was doing me to death by inches. I feel the effect of everyone of those hours in my side now; and for that cause, though he has done me many services, though I know his love and friendship for me, though at this moment I should be without pence were it not for his assistance, I will never see or speak .to him until we are both old men, if we are to be. I will resent my heart having been made a football. You will call this madness. I have heard you say that it was not unpleasant to wait a few years - you have amusements - your mind is away - you have not brooded over one idea as I have, and how should you? You are to me an object intensely desireable - the air I breathe in a room empty of you is unhealthy. I am not the same to you - no - you can wait - you have a thousand activities - you can be happy without me. Any party, any thing to fill up the day has been enough. How have you pass'd this month? Who have you smil'd with? All this may seem savage in me. You do not feel as I do--you do not know what it is to love - one day you may - your time is not come. Ask yourself how many unhappy hours Keats has caused you in Loneliness. For myself I have been a Martyr the whole time, and for this reason I speak; the confession is forc'd from me by the torture. I appeal to you by the blood of that Christ you believe in: Do not write to me if you have done anything this month which it would have pained me to have seen. You may have altered - if you have not - if you still behave in dancing rooms and other societies as I have seen you - I do not want to live - if you have done so I wish this coming night may be my last. I cannot live without you, and not only you but chaste you; virtuous you. The Sun rises and sets, the day passes, and you follow the bent of your inclination to a certain extent - you have no conception of the quantity of miserable feeling that passes through me in a day. Be serious ! Love is not a plaything - and again do not write unless you can do it with a crystal conscience. I would sooner die for want of you than....
Yours for ever
The story of John Keats and Fanny Brawne is one of literary tragedy. Keats, a leading poet of the nineteenth century, produced such influential works as Ode on a Grecian Urn and the epic poem, Hyperion during his short life. Keats met Fanny in November of 1818 and fell instantly in love with her, to the dismay of both her family and his contemporaries. The couple became secretly engaged soon after. However, in the winter of 1820 Keats became very ill. He was diagnosed with tuberculosis. Keat's health progressively declined and in a final effort to save his own life, he moved to Italy. In 1821, at the age of 25, he was laid to rest. Buried with him, close to his heart, was an unopened letter...from Fanny.
Content copied from http://www.theromantic.com/LoveLetters/keats3.htm and http://www.englishhistory.net/.