Fear is a Connection Obstacle. Fear either blocks Connection outright or causes one to shut down an already established connection.
List of Connection Obstacles
Connection Obstacles > Egotism, Fear, Hypocrisy, Interference, Passion, Resentment, Three Poisons, Toxic Attachment, Undisciplined Mind, Wrong Action, Wrong Environment, Wrong Thought
One REdditor describes an experience that caused them to doubt their sanity and "turn from the path."
Through all this time, however, Oona felt a heaviness in her heart. She said, "Mother, I have not dreamed. I cannot dream...." Mother said, "They will come. Then you will know. It is because you are fearful now that the dreams do not come.
St. Teresa of Avila notes that the sometimes intentional and sometimes ignorant imposition of fear, blocks access and prevents people from practicing Connecion Techniques, like prayer."Cease, as I have said, to have fear where no fear is; if any one attempts to frighten you, point out the road to him in all humility."
Tolstoy notes that fear of the unknown is a driver of disjuncture. He quotes Herzen, who refers to both fear and Disjuncture. Here, the pain of disjuncture is the motivation to overcome fear, pierce through Hypocristy, and move towards Alignment: "If you are content with the old world, try to preserve it, it is very sick and cannot hold out much longer. But if you cannot bear to live in everlasting dissonance between your beliefs and your life, thinking one thing and doing another, get out of the medieval whited sepulchers, and face your fears. I know very well it is not easy.
People "often carry fear with them as they begin to experience deeper layers of their own spiritual existence." 
- ↑ See https://www.reddit.com/r/mysticism/comments/okumxa/does_anyone_here_experience_things_that_made_them/
- ↑ Ignatia Broker, Night Flying Woman: An Ojibway Narrative (Minnesota: Minnesota Historial Society Press, 1983: p. 69).
- ↑ St. Teresa of Avila. The Way of Perfection. New York: Dover Publications, 2012. https://amzn.to/2Id75es.
- ↑ Tolstoy, Leo. The Kingdom of God Is Within You (Classics To Go) EBook: Leo Tolstoy: Amazon.ca: Gateway. Translated by Constance Garnett. CreateSpace, 2016. https://amzn.to/2Dg2jtj.
- ↑ Stevens, Petey. Opening up to Your Psychic Self. Nevertheless Press, 1983. p. iii