Sri Chinmoy: The worst impurity is a negative thought. When you are impure, you think, “I cannot do it. I cannot do the right thing. I cannot think of God or meditate on God. I cannot see the Light or the Truth.” This is doubt. It is the worst possible impurity.
We always have to see the light in a positive way. I may say that I have light in a very tiny, infinitesimal measure. But if I say, “I don’t have any light at all. All I have is darkness,” then I am fooling myself. Again, if an ordinary human being says that he has abundant and boundless light, then he too is fooling himself.
If you think that you have no light at all and that you are all darkness, this is false modesty and self-deception. False modesty and self-deception will never lead us to God-realisation. If you constantly think, “I am impure, I am insincere,” then you really become impure and insincere. Somebody may say to you, “I am impure,” but when he says this, he feels in the back of his mind that he is at least one iota more sincere than his neighbour, his friend, or somebody else. He tries to make others think he is sincere by exercising his false modesty. In this way insincerity also comes from impurity. So insincerity, imperfection and negative thought are all forms of impurity.
When we see something inside ourselves, we try to exhibit it outwardly. If I have insincerity inwardly, then I demonstrate it outwardly also. That is to say, if I have insincerity inwardly, then I will take refuge outwardly in the house of insincerity. But if I am sincere and pure inside, then outwardly I will take shelter in the house of purity and sincerity.
So the worst impurity includes negative ways of thinking, insincerity and the feeling of unworthiness. All these negative qualities are self-imposed.