Be wise as thou art cruel; do not press
My tongue-tied patience with too much disdain;
Lest sorrow lend me words, and words express
The manner of my pity-wanting pain.
If I might teach thee wit, better it were,
Though not to love, yet love to tell me so,
As testy sick men, when their deaths be near,
No news but health from their physicians know.
For, if I should despair, I should grow mad,
And in my madness might speak ill of thee;
Now this ill-wresting world is grown so bad,
Mad slanderers by mad ears believed be.
That I may not be so, nor thou belied,
Bear thine eyes straight, though thy proud heart go wide.
In plain English
You're cruel, but you're also intelligent—so use that intelligence. Don't push my patience any further with contempt. If you do, sorrow will give me words, and those words will describe exactly how much pain I'm in and how little pity you show me.
What I'm asking is simple: if you won't actually love me, at least tell me you do. It's like a dying man whose doctors only tell him he's getting better—a necessary lie that keeps him sane. Because if I lose hope, I'll go mad, and mad people say cruel things.
The world is twisted enough that mad insults get believed by mad ears. So for both our sakes—so I don't become that person, and so you don't end up slandered—just look straight ahead. Keep your eyes honest, even if your heart wanders elsewhere.