The poem you are referring to is likely "Dark Night of the Soul" by St. John of the Cross. This renowned work is a spiritual poem that explores the journey of the soul toward a union with God. St. John of the Cross, a Spanish mystic and Carmelite friar, wrote this poem during the late 16th century.

The concept of the "dark night" in the poem symbolizes the mysterious and unknowable nature of God, drawing inspiration from earlier mystical writings, such as The Cloud of Unknowing, which dates back to the 14th century. Both St. John's poem and The Cloud of Unknowing are influenced by the teachings of Pseudo-Dionysius the Areopagite, a mystical theologian from the 6th century.

The term "dark night" does not primarily refer to the challenges and hardships of everyday life but rather to the inherent obscurity and incomprehensibility of the divine path. The poem emphasizes the idea that the journey toward God involves a profound transformation and purification of the soul, often through a period of spiritual darkness or detachment from worldly attachments.

While there is uncertainty regarding the exact time and place of the poem's composition, it is thought to have been written between 1577 and 1579. Some scholars have suggested that St. John of the Cross may have composed the poem during his imprisonment in Toledo, although explicit evidence supporting this claim is limited and indirect. Nonetheless, "Dark Night of the Soul" remains a significant work in Christian mysticism, exploring themes of spiritual ascent, purification, and the profound encounter with the divine.