A lecture about English
A linguistics professor was lecturing to his English class one day. "In English," he said, "A double negative forms a positive. In some languages, though, such as Russian, a double negative is still a negative. However, there is no language wherein a double positive can form a negative."

A voice from the back of the room piped up, "Yeah, right."

A sudden change of mind
My Dearest Susan,

Sweetie of my heart. I've been so desolate ever since I broke off our engagement. Simply devastated. Won't you please consider coming back to me? You hold a place in my heart no other woman can fill. I can never marry another woman quite like you. I need you so much. Won't you forgive me and let us make a new beginning? I love you so.

Yours always and truly,
John

P.S. Congratulations on you winning the state lottery.