You know, I listen to a lot of sermons, almost on a daily basis.. and they don't get as good as getting a revelation. Haha.
So I just got one which is pretty cool. Not too long ago, I received a prayer request for healing for another person. I start to notice the words that the person used. "I pray that God would heal her."
As soon as I read that, revelation came. IT IS God's will for us to be healed. Healing has happened already when Jesus died on the cross.
1 Peter 2:24 - "who Himself bore our sins in His own body on the tree, that we, having died to sins, might live for righteousness—by whose stripes you were healed."
Isaiah 53:5 - "But He was wounded for our transgressions,
He was bruised for our iniquities;
The chastisement for our peace was upon Him,
And by His stripes we are healed."
So it is God's will for us to be healed, and healing is done, complete, finished.
The question is, why then does a sick body doesn't show signs of health when we read those Scriptures in praying for healing?
Let's say that healing is like a written book. The story inside the book is finished, hence the reason why it's published. But the book won't be yours until you reach out to grab the book.
So healing is done, but your body won't show signs of health until you reach out and grab it. And how do we reach out to grab it? We call it in, or we could also command the Hand of God to bring healing into our domain and that's when you know the difference between whether if it's God's will or not for you to be healed. In other words, when you know it's God's will, you will start to speak words of faith such as commanding the Hand of God to move in your life, and that's when you are activating faith - and faith move mountains, faith brings things to pass. If you're still asking to be healed, then you're in doubt because you only ask when you're not sure if the thing you're asking for is yours or not. Sometimes it takes awhile to convince your mind that you are healed, so until then, keep speaking the Word regarding healing as the Word is God's Word, and God's Words are always faith words!!! 
Wow. I'm starting to sound like the preachers I listen to.
There's a difference between command and demand. When you command the Hand of God to bring things into your domain, that's when you are (more or less) maneuvering God's Hand to do something for you. But when you demand, it's showing authority and you can't demand God to do anything because you have no authority over God.
I know there are some Christians who doesn't believe in healing.. and prosperity in every area of their lives, and that's ok. But I like victorious living, it's far better than living in poverty of every area of your life 