The unfolding of powers belongs to the side of consciousness; purification of bodies belongs to the side of matter. You must purify each of your three working bodies–mental, astral and physical. Without that purification you had better leave yoga alone. First of all, how shall you purify the thought body? By right thinking.
Then you must use imagination, your great creative tool, once more. Imagine things, and, imagining them, you will form your thought-body into the organisation that you desire. Imagine something strongly, as the painter imagines when he is going to paint. Visualise an object if you have the power of visualisation at all: if you have not, try to make it. It is an artistic faculty, of course, hut most people have it more or less. See how far you can reproduce perfectly a face you see daily. By such practice you will be strengthening your imagination, and by strengthening your imagination you will be making the great tool with which you have to practice in Yoga.
There is another use of the imagination which is very valuable. If you will imagine in your thought-body the presence of the qualities that you desire to have, and the absence of those which you desire not to have, you are half-way to having and not having them. Also, many of the troubles of your life might be weakened if you would imagine them on right lines before you have to go through them. Why do you wait helplessly until you meet them in the physical world. If you thought of your coming trouble in the morning, and thought of yourself as acting perfectly in the midst of it (you should never scruple to imagine yourself perfect), when the thing turned up in the day, it would have lost its power, and you would no longer feel the sting to the same extent. Now each of you must have in your life something that troubles you. Think of yourself as facing that trouble and not minding it, and when it comes, you will be what you have been thinking. You might get rid of half your troubles and your faults, if you would deal with them through your imagination.
As the thought body, becomes purified in this way, you must turn to the astral body. The astral body is purified by right desire. Desire nobly, and the astral body will evolve the organs of good desires instead of the organs of evil ones. The secret of all progress is to think and desire the highest, never dwelling on the fault, the weakness, the error, but always on the perfected power, and slowly in that way you will be able to build up perfection in yourself. Think and desire, then, in order to purify the thought body and the astral body.
And how shall you purify the physical body? You must regulate it in all its activities–in sleep, in food, in exercise, in everything. You cannot have a pure physical body with impure mental and astral bodies so that the work of imagination helps also in the purification of the physical. But you must also regulate the physical body in all its activities. Take for instance, food. The Indian says truly that every sort of food has a dominant quality in it, either rhythm, or activity, or inertia, and that all foods fall under one of these heads. Now the man who is to be a yogi must not touch any food which is on the way to decay. Those things belong to the tamasic foods–all foods, for instance, of the nature of game, of venison, all food which is showing signs of decay (all alcohol is a product of decay), are to be avoided. Flesh foods come under the quality of activity. All flesh foods are really stimulants. All forms in the animal kingdom are built up to express animal desires and animal activities. The yogi cannot afford to use these in a body meant for the higher processes of thought. Vitality, yes, they will give that; strength, which does not last, they will give that; a sudden spurs of energy, yes, meat will give that; but those are not the things which the yogi wants; so he puts aside all those foods as not available for the work he desires, and chooses his food out of the most highly vitalised products. All the foods which tend to growth, those are the most highly vitalised, grain, out of which the new plant will grow, is packed full of the most nutritious substances; fruits; all those things which have growth as their next stage in the life cycle, those are the rhythmic foods, full of life, and building up a body sensitive and strong at the same time.