We saw that reminding ourselves of our divine Self and repeating God's name are the best means to gain purity of mind. Along with these disciplines we must consider some important factors that influence purity of mind.
Purity of food: The Chandogya Upanishad (7.26.2) explains the role of food in effecting purity of mind: "When the food is pure the mind becomes pure. When the mind is pure the memory becomes firm. When the memory is firm all ties are loosened." According to Sri Ramanuja, there are three kinds of defects in food. First is the kind of food itself. Says Swami Vivekananda, "All exciting food should be avoided, as meat, for instance....Eating meat is only allowable for people who do very hard work, and who are not going to be Bhaktas; but if you are going to be Bhaktas, you should avoid meat....Any food that has been standing for days, till its condition is changed, any food whose natural juices have been almost dried up, any food that is malodorous, should be avoided." Second is the person who brings the food. In the words of Swami Vivekananda, "It is supposed that a man's character emanates from him, as it were, like a physical force, and whatever he touches is affected by it. So we must take care who touches our food when it is cooked. A wicked or immoral person must not touch it." Third are other instrumental causes like dirt and dust in food.
Monitoring our senses and mind: In explaining the above passage from the Upanishad, Sri Shankaracharya defines food as anything that is taken in by the senses: sound, touch, sight, taste, and smell. All these five perceptions leave impressions in the mind, and may add to the existing impurities. So we must discriminate about what we take in through the senses. More important are the ideas we collect in the mind. For example, we are to be careful about what we read and the company we keep. Besides deepening existing bad impressions, bad ideas can revive forgotten memories, agitate the mind and the senses, weaken our resolve, and lead us astray. Whatever produces impurities needs to be shunned. Says Swami Vivekananda, "Anything that makes you weak physically, intellectually, and spiritually, reject as poison; there is no life in it, it cannot be true."
The mind likes to be in a state of flux and randomness. It does not like order or discipline of any kind. Elevating thoughts do not arise in it spontaneously, only with effort and discipline. Instead of waiting for the mind to think elevating thoughts randomly amid so many useless thoughts, a wise seeker consciously practices thinking higher thoughts. Says Sri Ramakrishna, "Bondage is of the mind, and freedom is also of the mind. A man is free if he constantly thinks: 'I am a free soul. How can I be bound, whether I live in the world or in the forest? I am a child of God, the King of Kings. Who can bind me?'...By repeating with grit and determination, 'I am not bound, I am free', one really becomes so─one really becomes free."
Swami Vivekananda explains the power of thought: "The infinite future is before you, and you must always remember that each word, thought, and deed, lays up a store for you, and that as the bad thoughts and bad works are ready to spring upon you like tigers, so also there is the inspiring hope that the good thoughts and good deeds are ready with the power of a hundred thousand angels to defend you always and for ever."