Accept that and affirm that as Jesus preached the “kingdom of God is at hand” while traveling throughout Israel, he was always in the process of healing somebody, on the way to heal somebody, or had just come from healing somebody.
When I pray, I do use the words, “in accordance with God’s Will,” rather than “if God wills.”
How God chooses to heal is up to Him. He may choose to heal miraculously and instantaneously. The blind man was told to put mud in his eyes. The Book of Sirach tells us that the physician prays to God that his diagnosis may be correct.
Accept that the illness does not come from God.
Jesus often said, “Your sins are forgiven,” and only healed the person physically in order to bring people to faith, thus showing His ability to forgive sins. There was always a reason attached to the physical healing, as either an example of faith or to bring people to faith.
When lack of faith is mentioned as a reason for lack of healing, I point to St. Paul. “In weakness, power reaches perfection.” There may be a reason that a person of faith continues to have affliction, including developing greater empathy for others. I point also to the O.T. book of Job and the comforters who looked at Job as some poor sinner who deserved his fate. Putting God first is more important than being healed.