From John 15:7 we understand that it is God's will to heal everyone, because it is God's will to answer prayers. God promises to answer any prayer that lines up with His Word.
We know that healing lines up with God's Word because Psalm 107:20 tells us God sent His Word to heal us.
We know healing lines up with His Word because Matthew 9:35 tells us Jesus went through all the cities and villages, teaching, preaching, and healing every sickness and disease among the people.
We know healing lines up with His Word because Hebrews 13:8 says Jesus is the same yesterday, today and forever.
Jesus said, "If you abide in Me and My words abide in you, you shall ask whatever you will and it shall be done."