I'm a writer, so I cannot write a poem for you because I'm afraid of losing the rights to my work. However, I can help you to come up with your own. What do you find peaceful and calm? Maybe a hike, swimming in a lake, writing, listening to music? When you do the thing you like, how does it make you feel? can you relate something to nature or something else? Like if you like music, can you see the notes floating like butterflies? That would be a simile because I used the word "like" when comparing the notes to butterflies. If I wanted to write a metaphor, it would be something like, "The notes, butterflies that float gently in the air"
Take something simple and expand on it. Add "fluff" to make the thought, or poem, longer.
Hope this helped!