The first step to purification of the heart is to guard the "seven candles" to prevent any unwholesomeness from accessing the brain by way of the seven entrances - mouth, 2 nostrils, 2 eyes and 2 ears. Once he guards the "seven candles", he can begin to serve Hashem with enthusiasm. Serving Hashem with enthusiasm purifies the heart.

Be aware - whatever reaches the brain by way of the "seven candles" is embedded there forever. There should therefore be a "No Entrance" sign at each portal of the brain to exclude anything that is not pure and wholesome.

Ears - whatever a person hears is recorded in his mind. He must therefore be extremely cautious in what he hears and listens to. He should avoid listening to slander, lies and heresy. He should try to maintain control over what he hears. Therefore, he shouldn't listen to news broadcasts, especially when the newscasters are not people with emuna. Newscasters and commentators frequently express opinions which are diametrically opposed to Torah outlook and therefore are detrimental to a person's emuna.

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Eyes - everything a person sees is not only recorded on the brain, but becomes part of the brain. A person who has images of filth and pornography on his brain, is a person with a filthy mind. And, as we've learned, a person is what his mind is.

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Nostrils - guarding one's nostrils entails avoiding the smell of women's perfume, idolatrous incense or unkosher food and the like. [...] [W]hen Moshiach comes, he'll be able to smell piety. Therefore, piety and fear of Hashem are also spiritual purifications of the nostrils.

Mouth - whatever a person utters is recorded in the brain. [...] [W]holesome speech is an indication of personal holiness whereas vulgar speech is a sign of blemished personal holiness.