St. John of the Cross (1542-1591)
John was a doctor of mystic theology, and the founde, of the Discalced Carmelites, along with St. Teresa of Avila. He served as the spiritual director and confessor for the entire convent under Teresa's rule. His mystic writings include The Ascent of Mount Carmel and The Dark Night of the Soul.

Reflections from the Saints

If you do not learn to deny yourself, you can make no progress in perfection.
– St. John of the Cross