To improve, writers reflect on the process of what happens as they write. On Day Poems, I've offered up the value of having a pen pal, sending a postcard, and making a card to give to someone. Try writing a poem about writing a letter. Doing so requires you to consider audience, setting, and character.
Writing is a solitary act. You enter into a relationship with your reader that is imagined before it's realized. Somewhere I read that a relationship exists before the people are there to fill it. In this way, writing is an act of faith. Writing a letter exemplifies that faith: you compose in the present moment something you hope will reach the hands of another at a later time. (If you've ever sent a letter and had it returned to you months later, then opened and read what you'd intended for the recipient, you've had that somewhat surreal experience of interiority, gotten a peek into your internal workings.)
Daily Prompt: Write a poem about writing a letter. For an example, read "Preparing a Missive," a poem I wrote while thinking about my Ohio pen pal. My thanks to elephant journal for publishing it this week.