You put it best as hard as it can be on our feelings and emotions...sometimes people are even guilt tripped into thinking they just didn't "pray enough" or have "enough faith" or something else that will push them away from God instead of drawing them in...who are we to know God's plans not just in our lives but in the lives of all human beings. To emphasize your point healing isn't always physical; emotional and spiritual healing can also take place when we as people generally look for a physical one. I know this is one of the most difficult truths I've had to come to terms with as a Christian...why some and why not others? Why the physical healing for one's parent and the death for another? In the end I don't think we will know but it just reminds us to put our faith and trust in God he is in control and knows what is best more so than we do.