Let me not to the marriage of true minds

Admit impediments. Love is not love

Which alters when it alteration finds,

Or bends with the remover to remove.

O, no, it is an ever-fixèd mark

That looks on tempests and is never shaken;

It is the star to every wand’ring barque,

Love’s not Time’s fool, though rosy lips and cheeks

Within his bending sickle’s compass come;

Love alters not with his brief hours and weeks,

But bears it out even to the edge of doom.

If this be error, and upon me prov’d,

I never writ, nor no man ever lov’d.

—William Shakespeare,
Sonnet CXVI

Kirk: Spock…I believe…I’m in love with

    Edith Keeler.

Spock: Jim, Edith Keeler must die.

—“The City on the Edge of Forever”