If a lamp has no cover a draft will put it out, but if the lamp is enclosed in a cover, it will not go out even if there is a gust of breeze. If a brazier has no screen it will get dusty, but if the brazier is screened it will not be fouled even by flying dust.
What I realize as I observe this is the Tao of safeguarding the foundation of consciousness. Our conscious awareness is like a lamp or a brazier; awareness of reality is like a lamp glass or a brazier screen. If conscious awareness is not covered and protected by awareness of reality, the discriminating spirit will use consciousness to produce illusions, so it will be influenced by objects. Then the artificial will be in charge, the real will withdraw; aberrant energy will cover up sane energy. Like a lamp being extinguished, like a brazier being fouled, we lose our original selves. If conscious awareness is mated with awareness of reality, and awareness of reality is used to control conscious awareness while conscious awareness is used to follow awareness of reality, then the discriminating spirit has no way to emerge, the energy of consciousness has no way to fly. When the root basis is firm and stable, it may enter water without drowning, enter fire without burning. No pernicious external influences can harm it. This is like when a lamp has a cover and so does not go out, like a brazier that has a screen and so is not fouled by flying dust.
— excerpted from Awakening To The Tao, by Liu I-Ming