Since I learnt these mantras during my reiki training, I use it when I need to make peace and serenity inside me.
These sounds make vibrations in all your body, every syllables makes waves on some cells of the body, what calms immediately.
The recitation of mantra helps to make a meditation of full consciousness, centered on a sound which we produce ourself. Contrary to others meditations where we concentrate on our 5 senses, or on the breath, for example.

Generally we learn these mantras in reiki, at the same time as symbols (that I cannot unfortunately quote, nor draw, at the risk that masters reiki become very angry!)
Nevertheless, even if many people think that we have to know the symbol and its meaning ti have an effect with the mantra, I do not agree, that is why today, I share with you, these sounds which calmed me.

To recite a mantra, I am standing up, very straight ahead, anchored well, my roots very far in the earth.
I inspire and expire several times until my breath becomes more ample, and on the expiration I recite the mantra. I insist on every syllable, which vibrates in the depths of my being.
I become aware in the pronunciation of every syllables of the effects which the sound gets in my body.
And I recite them until the peace returns in me.

Here are 3 mantras (I do not explain you from which symbols it come, i don’t want to irritated the “reiki world”)

O-A-ZÉ-O-NÉ (This one is my favorite, the most powerful for cells vibrations (for me), this mantra suppress time and space, i mean next mantras will act on your past and your futur wounds)

Éii-Éii-Ki (suppress all negativ in you)

O-KOU-Éii (The strength)

I recite them with a deep and vibrating voice (you can have impression that it’s not your voice anymore, as when you recite the “OM”)
If you need that I record the sound, I shall make it.

Informe me of effects on you when you will have tried them!