And wheresoever he taketh him, he teareth him: and he foameth, and gnasheth with his teeth, and pineth away: and I spake to Thy disciples that they should cast him out; and they could not. – Mark 9:18

The spirit which possessed this poor child was accustomed to throw him sometimes into the fire, and sometimes into the water. Just our condition; for our spirit has sometimes been thrown into the very fire of presumption, and at another season into the floods of despair. We have alternated between the cold of melancholy and the heat of self-conceit. We have at one time cried, “I love pleasure, and after it I will go;” and at another time we have said, “My soul chooseth strangling rather than life; I would not live always.” At the moment while the father was speaking, the poor boy was on the ground wallowing in dreadful paroxysms of his disorder, foaming at the mouth, and gnashing with his teeth. Satan had great wrath, because he knew that his time was short. When the Savior spoke, and bade the devil come out of him, the fiercest struggle of all took place; for the unclean spirit rent the child, and the most terrible cries were heard. Still the father said, “Lord, I believe.” Now, it may be, dear hearer, you are yourself full of great trouble, vexed and tormented with innumerable fears of wrath to come; a little hell burns within your soul, anguish unutterable has taken hold upon you, your heart is like a battlefield torn by contending hosts, which rush hither and thither, destroying on every side. You are yourself an embodied agony; you are like David when he said, “The pains of hell get hold upon me, I found trouble and sorrow.” Can you now believe? Will you now accept the word of the Most High? …Surely Christ Jesus is fit to be believed at all times, for, like the pole star, He abides in His faithfulness, let storms rage as they may. ~ C.H. Spurgeon

https://www.blueletterbible.org/Comm/spurgeon_charles/sermons/1033.cfm