The excesses of the passion of  romantic love has been an abnormal phenomenon found in the poetry and song from the Troubadours to the Romantics. This “transgressive love” (love that exceeds the accepted social and moral boundaries), has been conceived as  a “madness,” a “fever” or a “sickness” (i.e., “lovesickness”). However, the twelfth-century troubadours, who coined the term of fin' amor  (“refined love”), conceived of it as a great paradox of love; you couldn't have the beautiful “rose” (i.e., the beloved, such as “Rosebud”) without its wounding “thorns;” none of love's joys without its sorrows. In this sense, the suffering of an “unrequited love” for an unattainable lady was taken on with great acceptance. Thus, for the troubadours, the reigning god of love, Eros, is the arrow, the disease, and the cure. 

The following is from two troubadours:

“He knows little of love who does not await mercy, for love desires us to suffer and to wait; then in a little time love repairs and amends all the pain he has made us endure so long, and that is why I prefer to die having known true love than to live with a high heart empty of love, for so love fated me from the beginning.”  

“Blessed be the pains, the sorrows and the cares which I have long suffered cause of love. Because of them I taste a thousand times more intensely the good which love now makes me feel. So much do the ills of the past cause me to enjoy my present happiness that it seems to me that if there were no evil one would hardly be able to savor the good.  Thus evil enhances the good and therefore should be welcomed when it comes.”

So we find the same paradoxical ideal in Wolfram's epic romance Parzival. Trevrizent the hermit says to Parzival: 

“The spear had to be thrust into the wound; then one pain helped the other, and from this spear became blood-red... What wondrous things this poison can do. From sorrow they received their wages, for the spear which pierced their hearts to the core carried away their joy. Then in the constancy of their grief they were baptized anew.”

Then there's the following from Chreitien De Troyes, the great medieval writer of the Arthurian romances: 

“From all other ills doth mine differ. It pleaseth me; I rejoice at it; my ill is what I want and my suffering is my health. So I do not see what I am complaining about; for my ill comes to me by my will; it is my willing that becomes my ill; but I am so pleased to want thus that I suffer agreeably, and have so much joy in my pain that I am sick with delight.”

The same sentiment can be found from a later Baroque poet in this love tradition, Richard Crashaw: 

“For in Love’s field was never found / A nobler weapon than a wound. /Love’s passives are his activ’st part, / The wounded is the wounding heart.”  

The Romantic poet Novalis carries this troubadour paradox of love into the 18th century and the Pre-Raphaelite poet, Dante Gabriel Rossetti, carries it into the 19th:

“Whoever flees pain / will love no more./ To love is always / to feel the opening / to hold the wound / always open.” 

“Beyond the sphere which spreads to widest space / Now soars the sigh that my heart sends above ; / A new perception born of grieving Love / Guideth it upward the untrodden ways.” 

The Pulitzer Prize winning American playwright and novelist, Thorton Wilder, carries it into the 20th century:

“Without your wounds where would your power be? It is your melancholy that makes your low voice tremble into the hearts of men and women. The very angels themselves cannot persuade the wretched and blundering children on earth as can one human being broken on the wheels of living. In Love’s service, only wounded soldiers can serve. Physician, draw back.”  

Finally, this troubadour paradox of  love finds its champion in the 20th century with the modern troubadour, Leonard Cohen, who knows that even though  “The doctors working day and night / ... they'll never ever find that cure for love:” 

“… The thorn of the night in your bosom / The spear of the age in your side / Lost in the rages of fragrance / Lost in the rags of remorse / Lost in the waves of a sickness / That loosens the high silver nerves … // And leave no word of discomfort / And leave no observer to mourn / But climb on your tears and be silent / Like a rose on its ladder of thorns ….”  (“The Window” )