Mysterion

 The apostles, and early Christians never used the word "mysticism."  Today, I hear it often.  Most of the time it is used by "New Age" people looking for a feel good emotion.  I'm defining mysticism as uniting oneself with Jesus.  

The aim is to unite yourself in prayer to Jesus.  This takes patience and perseverance.  

The Greeks called their pagan rituals of initiation, mysteries because they didn't tell anyone what the initiation rituals consisted of.  (Think of initiation rituals in college fraternities.) St. Paul in talking to the Greeks called God's plan, Mysterion, trying to connect familiarity to the Greeks.  St. Paul spoke of the joy of sharing the Christian life.  The Mysterion was God's Secret Plan.  (Ephesians 3: 8-11)

It is from the word Mysterion that the word "mystic" comes from.  "Mystic" led to "mysteries" because this type of prayerful union with God led to participation in God's Secret Plan.  (Think of the Mysteries of the Rosary.)

Hence, this was the aim of prayer for the apostles and early Christians--mysticism--to be united with Jesus in His contemplation of the Father.

Mysticism is the love of the praying person preparing for a deep union with Christ.  Reading about God is not the end.  Reading and the resulting knowledge won't change the prayerful person for the better.  It's the experience of being loved by God, that will change the person. Pray for this.