I know of no way of expressing anything so soothingly as music. Whether my heart is full of praise or mourning, no way of pouring it out is so satisfying as song.
Song is not always easy, though. Music derives its power from movement. It's the distance of one note from another that sets its mood.
The piano marks that distance best. No instrument lets so many notes hang in the air at one time, or time them so exactly. The guitar lets you do some of the same things with a little less precision, but with more freedom. You can bend the strings, and wander to tones between the notes, setting up tensions that the human understands.
The only problem with these instruments is that they take years of learning, two hands, and constant concentration.
The harmonica, on the other hand, does all that and lets me think more about what the music's saying than about how to say it. The harmonica is the lazy-man's guitar -especially in that it lets me bend for notes between the notes.
There's something about having the music I make three inches away from my ears that makes every note a prayer.
Duke Ellington or some such was playing the sax and stopped in the middle of a song one day. He looked up, and told the audience that he had forgotten the words. The same works for me. As I play, "It Is Well With My Soul," I am declaring it.
So, a word or two about the harmonica itself.
The first key skill is just learning to play one note at a time. The easiest way is to cover 4 holes with your lips, then block three of them with your tongue. It takes a little getting used to, but it's easy to do.
The next thing to learn is where the notes are. Blowing into the 4th hole gives you the note of C. (On a C harmonica.) Drawing and blowing on up the holes will give you the major scale.
What makes the harmonica sound cool, though, is playing the key of G on a a C harmonica. To do that, you have to start back on the 2nd hole, and make some notes that aren't naturally there by bending the note above them down a little bit. Once you learn to do that, you'll be amazed at how harmonica-y you sound.
If you like to express yourself in song, but don't have years to dedicate hours a day to refining and keeping you skills, I cannot recommend the harmonica too highly.