There is a conversation Jesus had with a desperate father whose son has been terrorized and controlled by a particularly vicious demon that had attempted to kill him through convulsions during which he tried to burn him to death or drown him. The poor father had been having to deal with this malignant spirit since the youth's childhood.
He first encountered Jesus; disciples who, one one occasion, Jesus had given them His authority to cast out demons but this time they had been humiliated--they failed. Jesus arrives, meets the father and demands that they bring the boy to Him. The following conversation ensues:
"They brought the boy to Him. When he saw Him, immediately the spirit threw him into a convulsion, and falling to the ground, he began rolling around and foaming at the mouth. 21 And He asked his father, “How long has this been happening to him?” And he said, “From childhood. 22 It has often thrown him both into the fire and into the water to destroy him. But if You can do anything, take pity on us and help us!” 23 And Jesus said to him, “‘If You can?’ All things are possible to him who believes.” 24 Immediately the boy’s father cried out and said, “I do believe; help my unbelief.”
And there is that wonderful verse of encouragement: "I do believe; help my unbelief!" We live in a fallen world in which perfection is not within our grasp. From the father's statement we learn that our faith will never be perfect in this life. As the hymn writer, Arthur A. Luther, wrote,
"Earthly friends may prove untrue,
Doubts and fears assail;
One still loves and cares for you,
One who will not fail."
The world, the flesh, and the devil may cause us to fear and doubts may assail, but our salvation based on Christ alone thorough faith alone, imperfect and wavering that faith may be, we are kept by the One who loves us still, the One who cannot fail.
The rest of the story?
"Jesus rebuked the unclean spirit, saying to it, “You deaf and mute spirit, I command you, come out of him and do not enter him [c]again.” 26 After crying out and throwing him into terrible convulsions, it came out; and the boy became so much like a corpse that most of them said, “He is dead!” 27 But Jesus took him by the hand and raised him; and he got up."
When fears and doubts assail, wrap yourself in Mark 9:24-27.