St. Teresa of Avila wrote the book the Interior Castle, inspired by her vision of the soul. The soul is like a castle made exclusively of diamond containing seven mansions, which she interpreted as the journey of faith through seven stages, ending with union with God and perfect peace.
From the center of the soul, God is calling...
1. Enter within yourself by prayer and meditation. Begin with the intention of becoming aware as you pray and listen to the Magnificent One.
The castle as described in St. Teresa's book is the soul. And in order to enter the first mansion you must enter within yourself through prayer. "I am reaching out to the souls who ultimately will enter the castle. Even if they are somewhat absorbed in the world, their intentions are good. Every once in a while they do try to put themselves in God's hands and reflect on who they are, even if they do not linger in their meditations," said St. Teresa of Avila.
2. Tune out the clamor of the world and tune into the delicate voice of God.
You begin to hear God in the form of meaningful conversations with other souls on the path, through inspiring speeches, and through sacred literature. God's light is a little warmer and brighter here in the second mansion.
3. Begin to practice spiritual discipline seriously by surrendering your own personal will to the will of God.
It's important in this mansion to quit trying to figure God out with our mind and concentrate on feeling him with our heart, if you can learn to surrender your personal will to the will of God, you progress to the next step or the fourth mansion.
4. The soul's part will become increasingly less and God's part increasingly greater.
"Leave your soul in God's hands. Let him do whatever he wants. Detach as radically as you are able from your own benefit and surrender to the will of God." - St. Teresa of Avila
5. The soul becomes engaged to marry God.
When the soul emerges from this state, it is left without a shred of doubt that "she was in God and God was in her."
6. The soul and God get to know one another better.
Lover and Beloved see each other for long periods at a time, and as they grow in intimacy the soul receives increasing favors, together with increasing afflictions. They may be bodily sickness, persecution, underserved praise or over-scrupulous spiritual direction. The soul experiences this love as a searing wound. Sometimes the pain is expressed as unbearable longing.
Still, the soul's suffering is infused with an effable happiness. And healing comes in the seventh mansion.
7. The soul reaches complete union with God, and the self is annihilated. Their is only love and perfect peace.
The soul is so glorious that God himself chooses it as his dwelling place. The path to God, then, leads us on a journey of self-discovery. To know the self is to know God.
Source: The Interior Castle by St. Teresa of Avila, translation and introduction by Mirabai Starr.