This is a tough subject, but I think the above is the core of the matter. The belief that God promises to heal every time as long as we cooperate is flawed IMO. If this were the case there would be no need of a gift of healing.
Originally Posted by apothanein kerdos
This belief stems from the doctrine that the atonement is always efficacious for physical healing in exactly the same way as it is for salvation. In other words, God has already done His part to heal us and if we aren't healed the problem is that we haven't received His promise in faith.
I know that everyone will not agree theologically with the following characterization, but look at what happens when I replace heal with save in my statement that I made above: God has already done His part to save us and if we aren't saved the problem is that we haven't received His promise in faith. Whether one believes in synergism or monergism in soteriology, the thought is still the same IMO: Physical healing is not a promise or grace of God equal with salvation (eternal life).
With that said, I believe we can, should, and are encouraged to approach God for grace in our time of need, and that includes for healing and on the behalf of others IMO. We are able to approach God boldly because of the atonement and because of the work of the cross on our behalf:
Hebrews 4:15 For we have not an high priest which cannot be touched with the feeling of our infirmities; but was in all points tempted like as we are, yet without sin.
16 Let us therefore come boldly unto the throne of grace, that we may obtain mercy, and find grace to help in time of need.
I Samuel 3:10 And the LORD came, and stood, and called as at other times, Samuel, Samuel. Then Samuel answered, Speak; for thy servant heareth.