Full Question

I've been having trouble lately defending the practice of praying for those who are sick. Praying that those who are ill and their loved ones would accept God's will, whatever that may be—that type of prayer makes sense to me. But doesn't praying for someone's healing imply that we have some control over God's will? If God felt it was time to bring a sick person home to him, would everyone's prayers for healing somehow change God's mind, as if what we wanted was better for the world than God's plan? And if prayer can accomplish that, it seems unfair to the sick person who has no one to pray for him.