Teresa of Ávila, also called Saint Teresa of Jesus, was a Spanish noblewoman who felt called to convent life in the Catholic Church. A Carmelite nun, prominent Spanish mystic, religious reformer, author, theologian of the contemplative life and of mental prayer, she earned the rare distinction of being declared a Doctor of the Church, but not until over four centuries after her death. Active during the Catholic Reformation, she reformed the Carmelite Orders of both women and men. The movement she initiated was later joined by the younger Spanish Carmelite friar and mystic John of the Cross. It led eventually to the establishment of the Discalced Carmelites. A formal papal decree adopting the split from the old order was issued in 1580.

Her written contributions, which include her autobiography, The Life of Teresa of Jesus and her seminal work The Interior Castle, are today an integral part of Spanish Renaissance literature. Together with The Way of Perfection, her works form part of the literary canon of Christian mysticism and Christian meditation practice, and continue to attract interest from people both within and outside the Catholic Church.

Forty years after her death, in 1622, Teresa was canonized by Pope Gregory XV. However, not until 27 September 1970 did Pope Paul VI proclaim Teresa the first female Doctor of the Church in recognition of her centuries-long spiritual legacy to Catholicism.
Source: https://en.wikipedia.org/wiki/Teresa_of_Ávila

"It is no small pity, and should cause us no little shame, that, through our own fault, we do not understand ourselves, or know who we are. Would it not be a sign of great ignorance, my daughters, if a person were asked who he was, and could not say, and had no idea who his father or his mother was, or from what country he came? Though that is great stupidity, our own is incomparably greater if we make no attempt to discover what we are, and only know that we are living in these bodies, and have a vague idea, because we have heard it and because our Faith tells us so, that we possess souls. As to what good qualities there may be in our souls, or Who dwells within them, or how precious they are--those are things which we seldom consider and so we trouble little about carefully preserving the soul's beauty. All our interest is centred in the rough setting of the diamond, and in the outer wall of the castle--that is to say, in these bodies of ours."
Excerpt: Interior Castle

   Interior Castle The Life of Teresa of Jesus  The Way of Perfection