The mind is almost always impure, and it almost always brings in unaspiring thoughts. Even when it is not doing this, the mind is still a victim to doubt, jealousy, hypocrisy, fear and other undivine qualities. All negative things first attack the mind. The mind may reject them for a minute, but again they knock at the mind's door. This is the nature of the mind. The heart is much, much purer. Affection, love, devotion, surrender and other divine qualities are already there in the heart. That is why the heart is much purer than the mind. Even if you have fear or jealousy in the heart, the good qualities of the heart will still come forward.
But again, the heart may not be totally pure because the vital being is near the heart. The lower vital, which is situated near the navel, tends to come up and touch the heart centre. It makes the heart impure by its influence and proximity. But at least the heart is not like the mind, which deliberately opens its door to impure ideas. The heart is far better than the mind. And best is the soul. The soul is all purity, light, bliss and divinity.
In order to purify your mind, the best thing to do is to feel every day for a few minutes during your meditation that you have no mind. Say to yourself, "I have no mind, I have no mind. What I have is the heart." Then after some time feel, "I don't have a heart. What I have is the soul." When you say, "I have the soul," at that time you will be flooded with purity. But again you have to go deeper and farther by saying not only, "I have the soul," but also "I am the soul." At that time, imagine the most beautiful child you have ever seen, and feel that your soul is infinitely more beautiful than that child.
The moment you can say and feel, "I am the soul," and meditate on this truth, your soul's infinite purity will enter into your heart. Then, from the heart, the infinite purity will enter into your mind. When you can truly feel that you are only the soul, the soul will purify your mind.
Before you meditate, try to imagine a flame inside your heart. Right now the flame may be tiny and flickering; it may not be a powerful flame. But one day it will definitely become most powerful and most illumining. Try to imagine that this flame is illumining your mind. In the beginning you may not be able to concentrate according to your satisfaction because the mind is not focused. The mind is constantly thinking of many things. It has become a victim of many uncomely thoughts. The mind does not have proper illumination, so imagine a beautiful flame inside your heart, illumining you. Bring that illumining flame inside your mind. Then you will gradually see a streak of light inside your mind. When your mind starts getting illumined, it will be very, very easy to concentrate for a long time, and also to concentrate more deeply.
Before you start your a meditation, repeat "Supreme" about twenty times s as fast as possible in order to purify your breath. Feel s that you are really growing into the very Breath of God. Unless and until the breath is purified, the mind will not s remain one-pointed.
Focus your attention on a picture. You can look at your Master's picture or you can look at yourself in the mirror. If you concentrate on your own reflection, feel that you are totally one with the physical being that you are seeing. Then try to enter into the image that you are seeing. From there you should try to grow with one thought: God wants you and you need God. Repeat: "God wants me, I need God. God wants me, I need God." Then you will see that slowly, steadily and unerringly this divine thought is entering into you and permeating your inner and outer existence, giving you purity in your mind, vital and body.
You can tell your mind, "I shall not allow you to go in your own way. Now I want to think of God." Repeat the name of God inwardly or aloud. Then say, "I want to have purity in my whole existence." Then repeat "purity, purity, purity." At that time you are not allowing your mind to think of impurity or of any other thing. Don't give your mind a chance to wander; simply utilise your mind for your own purpose. You have millions of things to accomplish in and through the mind. But the mind is so naughty and mischievous that if you don't utilise it, it will utilise you.
Each time an undivine thought enters into your mind, throw it out of your mind. It is like a foreign element, a thief, that has entered your room. Why should you consciously allow a thief to remain in your room when you have the capacity to throw him out? When an undivine thought enters into your mind, just capture the thought and throw it into the blazing fire of your inner aspiration.
When a thought comes that is not pure, good or divine, immediately repeat the word "Supreme" very fast. The Supreme is my Guru, your Guru, everybody's Guru. Repeat "Supreme" very fast, and each time you use the word "Supreme," feel that you are creating a snake that will coil around the undivine thought and strangle it.