Valentine from "The Two Gentlemen of Verona" (Act III), by William Shakespeare

“To die, is to be banish'd from myself;
And Silvia is myself: banish'd from her,
Is self from self: a deadly banishment!
What light is light, if Silvia be not seen?
What joy is joy, if Silvia be not by? 
Unless it be to think that she is by,
And feed upon the shadow of perfection.
Except I be by Silvia in the night,
There is no music in the nightingale;
Unless I look on Silvia in the day,
There is no day for me to look upon;
She is my essence, and I leave to be,
If I be not by her fair influence
Foster'd, illumin'd, cherish'd, kept alive.”