The Psalms were created for worship. They’re a collection of songs and poems that demonstrate a full range of honest emotions and show what a relationship with God looks like. Most, but not all, of the Psalms, were written by David. We can learn a lot
"I bought a nice leather journal for my missionary and wrote these on the first two pages. He loves it and tells me all the time how comforting these scriptures are!" Sounds like this might be handy to have.