Look at your PERSONAL PLAN FOR DEVELOPING mastery of the instrument and knowledge of music as a pyramid.
A pyramid made of stone like the ones in Egypt. The base is very wide, and the top is at the point. Where you go in music depends on the strength of the FOUNDATION stones you lay at the BASE OF THE PYRAMID.

If you master these skills, you can go far. And if you don’t you’ll pretty much be a beginner forever.

If you think about it…in its essence…the harmonica is a BREATH instrument, like a trumpet, or clarinet, or flute. But unlike any other instrument, it relies both on breathing in and breathing out. Your MASTERY of breathing in and out is the very FIRST, and most important technique in your pyramid. What is good breathing technique? Well, it’s the ability to deliver the right amount of air, blowing or drawing, from your DIAPHRAM any time you need it, for as short or as long as you need it.

A lot of players think the breathing originates in the chest…it does not. It’s like a singer…your ENTIRE BODY body is your instrument. (I was a classically trained singer.) It starts with a stable position for your feet, and air goes in through the mouth or nose and mouth, pulled in by action of the diaphragm. If this not clear yet, put your hands on your tummy area, or diaphragm, and say “ho, ho,ho,” like Santa Clause, with short strong bursts of breath. The diaphragm is the beginning of good sound. Can you guess what the sound chamber is for the harmonica? It’s your mouth shape, and tongue position, open glottis at the back of your throat, open nasal cavities, and the long long air pathway to the bottom of your lungs, supported by a strong diaphragm. Think of it all as a long open tube, and the more open it all is the better the resonance of the sound. (Note that singers do better standing, you don’t see them in a studio sitting, guitarists sit, wind instrument musicians stand…because…yes, you guessed correctly… the DIAPHRAM works better standing). Your goal is to develop a totally relaxed breath, because music is beautiful and pleasing to the audience only when the musician IS RELAXED!

Place the harmonica in your mouth and using the pucker or tongue emboucher, just breath in and out, allowing the harmonica to sound. Just try and breath naturally, in…. and out…from your diaphragm. Your tummy area should expand and contract, rise and fall. Watch it, then feel it with your hands. The diaphragm area should move in and out. Let the notes build and fall in volume…in one long line of sound.

Do this for 5 minutes a day for a month.

Play one note blowing, play that note as quietly as you can, then increase the volume slowly until it’s a loud as you can play it.
How long can you play one note? Time it. Now do the same on a blow.

Play one note in short and quick bursts. You can control the air with your diaphragm, with quick movements of the diaphragmatic musculature, or you can use your tongue to block and unblock the hole. Try both.
Every day, when you start to play, spend a moment practicing breath.

What it takes to play a note in the mid-range of your chromatic harmonic is very different from what the lowest 4 holes require. The lower notes take a lot more breath. (Manufacturers even warn buyers that the low notes are hard to hit correctly, and may not sound well early on with a new harmonica because the player’s technique needs improvement.)
So let’s take the draw A on the third hole of a 16 hole chromatic. Draw and try to make a sound, work on that note every day, it’s a weak note for most players. Stop warbling, and make it a clean clear note. It will likely take some time.
The draw D on hole one and the draw F on hole two are also very challenging, as are the draw Bb slide in on hole 3, and the draw B on hole 4. Did you notice that they are all draws? Draws are much harder for beginner and intermediate players to control than blows. Why? Most people have blown some instrument in their lives, maybe a flutophone, or a wind instrument, or just whistling. You’ve blown up balloons, and blown out candles on cakes. But making music on a draw? The only time you’ve drawn air is to breath in. You can do it, but it’s not under great control.
When you talk, you are blowing. So you are used to controlling the amount of air on blows to some extent, not so much for the draws which is why they’ll need improvement.

Do the same exercise as Exercise #4 above, but play on the three other octaves, that would be holes 5-8, then 9-12, then special attention at 13-16. You’ll find that the second octave grouping of holes 5-8 and the third at holes 9-12 are pretty easy to play and get good sound and tone easily. However, the final octave at 13-16 will feel very different from the others, and you’ll want to take extra time on that last octave.

This reminds me of an experience I had with my alto saxophone and a wonderful jazz player who was giving me a lesson. He asked me to play many scales on the highest notes.
I did poorly, saying, “I don’t really play those notes,” boy was that the wrong answer!

For the harmonica player whose FOUNDATION STONE OF BREATH is solid, and dependable, like a rock made of granite, improvement as other skills sets are added is certain.
They can rise to the occasion and excel every time.

But for those who never master BREATH, and for whom the secrets of breath remain a secret, with a BREATH foundation stone crumbling like sandstone, harmonica becomes an extended vacation in the world of the beginner, and MASTERY evades them. Make a wise choice on breath, see if for the crucial skill set it is. MASTER it, and receive the benefits of same, and your FOUNDATION will stand for years. It will be the rock upon which your harmonica playing soars high overhead, as YOU enter the world of MASTER OF HARMONICA.