Sri Aurobindo
Letters of Sri Aurobindo
Volume 1
I was very glad to get your letter and especially to know that you are more at peace. That is what is first needed, the settling down of a natural peace and quiet on the nature – the spiritual peace is a bigger thing that can come afterwards.
Then as to concentration. Ordinarily the consciousness is spread out everywhere, dispersed, running in this or that 
direction, after this subject and that object in multitude. When anything has to be done of a sustained nature the first thing one does is to draw back all this dispersed consciousness and concentrate. It is then, if one looks closely, bound to be concentrated in one place and on one occupation, subject or object – as when you are composing a poem or a botanist is studying a flower. The place is usually somewhere in the brain, if it is the thought, in the heart if it is the feeling in which one is concentrated. The yogic concentration is simply an extension and intensification of the same thing. It may be on an object as when one does trātak on a shining point – then one has to concentrate so that one sees only that point and has no other thought but that. It may be on an idea or word or a name, the idea of the Divine, the word OM, the name Krishna, or a combination of idea and word or idea and name. But, farther, in Yoga one also concentrates in a particular place. There is the famous rule of concentrating between the eyebrows – the centre of the inner mind, of occult vision, of the will is there. What you do is to think firmly from there on whatever you make the object of your concentration or else try to see the image of it from there. If you succeed in this, then after a time you feel that your whole consciousness is centred there in that place – of course for the time being. After doing it sometimes and often it becomes easy and normal.
I hope this is clear. Well, in this Yoga, you do the same, but not at that particular centre, but anywhere in the head or at the centre of the chest where the physiologists have fixed the cardiac centre. Instead of concentrating on an object, you concentrate in the head in a will, a call for the descent of the peace from above or, as some do, an opening of the unseen lid and an ascent of the consciousness above. In the heart centre one concentrates in an aspiration, for an opening, for the presence of the living image of the Divine there or whatever else is the object. There may be Japa of a name but, if so, there must also be a concentration on it and the name must repeat itself there in the heart centre.
It may be asked what becomes of the rest of the consciousness when there is this local concentration? Well, it either falls silent as in any concentration or, if it does not, then thoughts or other things may move about, as if outside, but the concentrated part does not attend to them or notice. That is when the concentration is reasonably successful.
One has not to fatigue oneself at first by long concentration if one is not accustomed, for then it loses its power and value. One can relax and meditate instead of concentrating. It is only as the concentration becomes normal that one can go on for a longer and longer time.