The trap the “mystics” fell into was they made their personal experience with God the ultimate goal of their life, and hence, unwittingly, put self at the center and became self-serving. Many modern charismatics have fallen into the same deception.
Perhaps some would be shocked to learn that spiritual experiences, though important, are not the ultimate goal of the Christian life. To love and glorify God, to know Him by faith, and to do His will is the ultimate goal: something for Him, not something for me: THIS is the ultimate goal.