The disciples of Jesus have just witnessed the miracle of the multiplication of the loaves and fishes for thousands of people, but their associative mind can not accept the reality of what it sees and experiences.
At any time the human mind accomplishes the psychic process of idolatry. What is idolatry? It is to consider what is unreal as real, and and consider what is real as unreal. The associative mind of the disciples, although having Jesus before its eyes, although having experienced His power and His greatness, His divine heavenly essence, sees Him as He were a ghost. The associative mind feeds itself on the inner dialogue of idolatry, that is it continuously inverts reality, at any time and in any circumstance of life. It is the inner dialogue of idolatry that keeps the human mind in the storm of doubt, in the storm of thinking ill of God and all that is in front of it, in a continuous turmoil which makes man believe that he has to go through life always struggling with pain and fatigue, constantly against the wind. Idolatry shows what is unreal as real and what is real as unreal, and this is a great trouble for humanity. This kind of mental hurricane of idolatry generates fear, the emotion that can destroy man, the favorite food of Satan that makes the Evil one strong and powerful.
What can replace the inner dialogue of idolatry? Faith, trust in God, in life, in love overcomes the idolatry of the mind. Trusting God with love and gratitude turns down the mental process of idolatry and turns on the mental process of intelligence. Faith, trust in God, does not make man religious but intelligent and fearless. Literally, Jesus' words which indicate the procedure to get rid of the mental process of idolatry are: Have faith, it is I, do not be afraid.
Have faith. The Greek verb is tharsèo or tharrèo (they are two different dialects), and it basically means "I dare, I act boldly," from which it derives: "I find the courage, I am serene." The more general meanings are: "to rely on someone or something, to trust, to be brave before someone or something, to face someone or something fearlessly." This verb uttered by Jesus gives solidity and security. Jesus gives the terrified disciples salvation but also safety, courage, peace.
Do not be afraid. It is an adverb of negation, mé, "not", coupled with the imperative aorist of phobèomai, "I am scared, I am afraid, I am taken and carried away by fear." The original meaning of this verb is "to escape, disrupt, defeat," it refers to an action which then creates the corresponding mood of "fear", that is phobòs. Jesus invites his disciples to trust Him always and incessantly, without ever turning the power and grace of His presence into a mental, ideological ghost. This is the only way to stop being afraid. Faith is the only psychic-spiritual force that can replace the mental process of idolatry and free man from fear.