Here’s an interesting quote by William Walker Atkinson:

“Without wishing to lead you into the subtleties of Oriental psychology, with its complicated forms of breathing for psychic and spiritual development, etc., I must call your attention, at this point, to the philosophy underlying some of the Oriental breathing practices, for the same is based on the soundest scientific principals. The Oriental philosophy teaches that each mental and physical state of the individual is represented by a special rhythm of breath, the rhythm and condition always being found together.

The mental or physical condition will invariably manifest the particular rhythm of breath, which belongs to it; and, likewise (and this is one of the occult secrets) the deliberate assumption of a particular rhythm of breath will speedily result in the manifestation of the appropriate physical or mental condition.

You have but to consider the subject for a moment, to see that when you are frightened or angry, you breathe with a different rhythm than when you are calm and peaceful. Each emotion, up and down the scale, has its own appropriate rhythm of breath, which invariably manifests at the same time. Moreover, different physical conditions like wise manifest in coordinated breath-rhythms. Keep a close watch on yourself, and those around you, and you will soon see that the above statements of facts are strictly correct. You will wonder why you never noticed the phenomena before.

A little less known, even, is the correlated fact that the deliberate assumption or “acting out” of the particular breath –rhythm related to a particular emotion, will result in a speedy experiencing of the emotion itself. This also may be tested out on yourself. You will find that a few moments’ anger-breath or fear-breath (if well acted out, or assumed faithfully) will result in you soon experiencing a feeling of anger or fear, as the case may be. Likewise, you will find that the deliberate assumption, on your part, of the breath-rhythm of peace, calm, self-control, will be sufficient to induce that particular state of feeling in you.

There is a big hint in this last sentence, by the way, for that is exactly what the Oriental sages do to induce and maintain the mental state of hilosophic calm for which they are noted.

In this connection, let us remind you that when you are endeavoring to control your temper, and to maintain your pose, under extreme provocation, you will find that you instinctively strive to control your breath-rhythm, which shows a marked tendency to fly off into a state of rapid panting and gasping. And, so long as you can maintain your steady controlled rhythm of breath, you will maintain your poise and self-control.

Well, to make a long story short – to get right down to the gist of the subject of the absorption of nerve-force through controlled breath-rhythm – let me say to you (1) that there is a breath-rhythm which nature uses to restore nerve force to the depleted system, after a great demand upon it in the direction of either a strong mental or emotional strain, or after a severe
physical strain; and (2) that a deliberate assumption or “acting out” of this particular breath-rhythm will result in your being able to quickly absorb a greatly increased supply of nerve-force for the purpose of use in personal magnetism – to render you full of physical magnetism, in fact.

Do you catch this point? If not, reread the above paragraph, several times, until you fully grasp the importance of the statements therein contained – for they comprise exactly on e-half of the philosophy of nerve-force generation – and much more besides if you are able to grasp it.”