The light of the divine is veiled so it doesn't blow out our circuits. Through middot practice, we take off our veils to manifest our true selves; and God veils God's self in order that we can apprehend God; and we meet in the middle. -- The Velveteen Rabbi
As we take off the veils, we move through these successive states, or worlds:
ASSIYAH, earth, the objective world, where we live with our bodies in the physical world of action, including action for spiritual purpose. This is the world of sensible, concrete facts and their data. Here we are conscious of the physical realm and the laws of nature as we observe them. Here we are aware of being a creation of God. This is the world of duality, in which everything is seen as separate, and subject to cause and effect. This is also the world of the life force, the senses, the breath, experiencing freedom and love of life, being the God-wrestler. Guf (body); Nefesh soul aspect.
YETZIRAH, water, the subjective world of vital feelings; the world of affect, of nuance, of aura, of sensitivity, of visceral and proprioceptive feelings. Things are seen as synchronistic in this world. This is the world of interdependence and relationship issues. Here is where our emotional being is attuned, where negative feelings of resentment, frustration, vindictiveness, and paranoia can be replaced by an attitude of gratefulness, appreciation, and joy. Here we can learn empathy, humility, and awareness of our own mortality. Ruach soul aspect.
BRIYAH, air, the symbolic world of the intellect, of contemplation, of pure thought. Everything is part of a pattern in this world; everything has a meaning. We understand ourselves as being the result of intended, loved, and continuous creation. Here we are commanded to exert ourselves to know and to reach the very edge of what is thinkable and understandable. This is the reality of poetry, wonder, intuition, and visualization. In this world, we can work with symbols and with dreams. Neshama soul aspect.
ATZILUT, fire, the holistic world of deep divine intuition and of beingness with God. Reality is merged; all is one. This is the world of essence, where we recognize ourselves as being a spark of God's fire. It is not we who pray; rather, God prays in us. With God's own eye we see ourselves. Chaya and Yechidah soul aspects.
The Four Worlds in Judaism