There's no doubt that God can heal people and it's a dramatic, permanent, and immediate event. But most of the time he doesn't. These faith healing ministries that prey on people's hopes as well as their wallets offer guaranteed healing, but it turns out to be a sham and people's hopes are cruelly dashed. It's arrogant to assume that God is a genie at our beck and call to dispense healing with the right ritual or incantation "in the name of jeee suss". And yet that doesn't mean it can't happen. With what boldness did Peter tell a crippled man, "I don't have silver and gold, but what I have I give to you. In the name of Jesus Christ of Nazareth, stand up and walk," knowing that it may not be God's will to heal that man. Or was Peter truly operating by the filling of the Holy Spirit, as I believe? I'm hard pressed to take advantage of people's desperation when I truly don't know but that God has a different plan for them than healing their body.
I often cite the healing of the paralyzed man lowered through a rooftop as an example of this. The first thing Jesus says is, "your sins are forgiven." People stood around wondering when Jesus was going to do something. We look for the flashy miracles, the dramatic healings, and dismiss as quotidian the real miracle of a soul translated to salvation.
I have a disease for which there will never be healing in this life. I've been through it all, people have prayed for me, layed on hands, used anointing oil, told me I just need to have faith, "claimed" a healing for me, etc. All to no avail. But what I found is that my trust in God deepened when I asked myself if I could trust in a God who said "no". What if I truly had to wait until heaven until the final and ultimate healing? Can I love God when he says "not now", can I trust him? Moreover, is it God that I love or the goodies that God dispenses?
Christians are not immune from suffering and many suffer cruelly. But we have the opportunity, instead of trying to escape suffering, to unite our sufferings with the sufferings of Christ for the conversion of sinners (see Colossians 1:24). We can allow it to draw us closer to God. We can consider that it may very well be that temporal healing is not in our best interest and be content with the hope of the healing to come.