William Shakespeare, Sonnet cxlvii
My love is as a fever, longing still 
For that which longer nurseth the disease; 
Feeding on that which doth preserve the ill, 
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The uncertain sickly appetite to please. 
My reason, the physician to my love, 
Angry that his prescriptions are not kept, 
Hath left me, and I desperate now approve 
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Desire is death, which physic did except. 
Past cure I am, now reason is past care, 
And frantic mad with evermore unrest; 
My thoughts and my discourse as mad men's are, 
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At random from the truth vainly express'd ; 
For I have sworn thee fair, and thought thee bright, 
Who art as black as hell, as dark as night.