"I wrote you a letter, actually. Two. Though I didn't know where to send it."
She said nothing in response to the opening.
"How did it make you feel?"
"On the surface, calm. Deeper than that, abandoned."
—from Abandon, a novel by Pico Iyer
For years I've written letters. Some get sent. Most do not.
A few years ago I began using letters as a writing prompt with students: Write a letter to your younger self. To someone you love. To someone you don't.
The exercise is cathartic, and creates a calm but poignant sadness. And almost always, the letters I do not send are seeds for the letters I finally do.