When reading St John of the Cross it is important to differentiate between his practical methodologies for the spiritual life and spiritual growth and his mystical poetry, very often they are describing the same thing in different terminology.
St John is a mystic and his mystical poetry can be challenging. Firstly, read the poem, as such and enjoy the poetry: the visual aspects, the feeling of the setting, the sounds, sights and environment he introduces. He is speaking of the soul’s ascent to God, to spiritual marriage; this marriage is not achieved overnight, in fact it is a long and, sometimes, arduous process. Understanding the poem and meditating upon the poetry is a step by step process. Allow the Holy Spirit to speak to you, upon whatever stage of the ascent you are on. As you proceed upon the path the mystical language will resonate more and more. The two symbols: the darkness and the cross, are figurative of union with Christ, of suffering but also of faith, which impatiently reaches for God, with longing, in the midst of unknowing. When you realize that the dark night is not a burden but rather a gift then you will crave the closeness to Christ that the way of darkness brings. In this we realize that the ineffable light of God is darkness to our mortal eyes, the eyes of the soul. It is about abandonment, abandonment to a loving God, abandonment to the Crucified Christ Who thirsts for us, abandonment to the all-powerful love of the Blessed Trinity.
God is not a thing to be seized, rather He is the Beloved seeking the Lover. In seeking God, God strips us of all encumbrances, until we stand before Him naked: as Christ was made naked for love of us. It is invaluable to seek the clarification and thoughts of students of Saint John; for me “The Science of the Cross” by St. Teresa Benedicta of the Cross (Edith Stein) was monumental in beginning to understand the holy father John. Also, read about the Saint’s life, the sufferings he underwent, the journey he made, where he was at each stage of his life as he wrote his great works. When you connect his personal life and the environment in which he lived with the works themselves you gain a greater appreciation for the gravity and the power of his awe inspiring words. Peace be with you.