The most sustained letter-writing (snail mail) I've ever engaged in was with a friend from Seattle, WA. He and I carried on a correspondence over a couple of years, averaging one or two letters a week, some lengthy. I have to say that writing back and forth that frequently meant we were conducting a friendship at a level much deeper and profound than many of the friendships I had face-to-face.
Our letters included poems, stories, philosophy, theology, cultural analysis, description. They ranged widely. I still remember one letter especially where he offered a kind of prayer based on a Psalm 46:10:
"Be still and know that I am God.
Be still and know that I AM.
Be still and know that...
Be still and know.
Be still and...
We both made use of this prayer as a kind of mantra, reminding ourselves that we can be still and know that God is. That God is "I Am Who I Am." That we can trust that. That we can simply rest in knowing that. That sometimes you can be still, and the "and" comes along in the stillness. Just be still. Just be.
My friend was more of a mystic, and so was happy to leave it at that. Myself, still irrepressibly Lutheran, I like to remember that I am called to be still, to just be, because that's the best response to know that we are justified for Jesus' sake. God does it, not us.
No matter how you frame, either theologically in terms of the proclamation of the Gospel, or apophatically, in the presence of God the I AM, it makes a great prayer, and I commend it for regular use.
As an addendum, I should add that my friend is now an Orthodox monk, and I am a Lutheran pastor. I believe that correspondence we conducted over the years helped shape our individual vocations. God can get in the middle of epistolary conversations and do a new thing.