What is the title of this German Love Poem?

My friend is trying to find a German love poem about unrequited love. She's not positive, but she thinks it's from a foreign Spanish film called the Dark Side of the Heart. In a certain scene of a movie (if it's from a movie) the man's poem goes along the lines of "not having you is worse than dying". Does anyone have any idea where this German love poem may be from? The poem was read in Spanish.