thanks for the email. I once heard Adrian Plass say 'We know two things about God and healing. First is that He heals. Second, is that He doesn't.' Not sure if it helps but it made me laugh and wasn't far from the truth! But to get into it, let me start by asking you a question... "What do you think is the ultimate purpose of God?" Ok, I didn't say it was easy! But what do you think it is? For whatever it is, it is obviously something that God desires and will work all things together to achieve. And I think if we can answer this question, then all the smaller questions concerning God's will for someone's health, wealth, and prosperity will be answered as well.
Here is what I believe is the ultimate purpose of God - the very essence of what God was after even from before the foundation of the earth -
'For those God foreknew he also predestined to be conformed to
the likeness of his Son, that he might be the firstborn among many brothers.' Rom 8:29
This verse obviously helps explain the verse before it which we all know -
'And we know that in all things God works for the good of those who love him, who have been called according to his purpose.' Rom 8:28
So according to these two verses, it is the purpose of God that Jesus would not only have many brothers, but that those who believe would be conformed to His likeness! This is the 'good' that God desires and works 'all things together' to achieve. So there will be times of rain, times of hail and times of sunshine, and all are used to develop the character of His Son in the believer. So yes, God will use ill-health and sickness sometimes to do this conforming.
I do not agree that 'Jesus desires us to be healed of all our sickness'. His purposes are far higher than our desire for a quick fix to our problems. Having said that, it is also sometimes definitely the will of God to heal us and He still does so wonderfully today. But that is why He is our Heavenly Father, faithful through good and hard times. He knows what is best for us, even when we don't.
I think God has given us the book of Job to show that even for those whom He calls 'blameless and upright', He still allows them to suffer (and Job's suffering included physical sickness) if it is part of His plan for the individuals greater good. There are many other examples we could look at - even from the New Testament.
The Apostle Paul - it was because of a 'bodily illness' that he ended up preaching to the Galatians. There is no hint that it was against the will of God that this happened or that if Paul had just had more faith he wouldn't have got sick at all! (Gal 4:13)
Timothy - He suffered from frequent stomach problems. Again, when this is addressed by Paul, he doesn't say 'Timothy, you are out of God's will! Just believe and it will go away!' No, Paul takes a very practical stance in the matter and simply says 'Stop drinking only water and use a little wine.' (1 Tim 5:23)
Other examples could be mentioned like Tropimus (2 Tim 4:20) or Epaphroditus (Phil 2:25-30). But never is there anything in these examples to suggest that they shouldn't have been sick! Unfortunately, because of all the faith-prosperity fakes around, there is confusion on this issue within the church.
There will come a day when we have new bodies and then all sickness and bodily suffering will be done away with. There will also come a day when God will create a new Heaven and a new Earth... on that day He will make all things new and 'He will wipe every tear from their eyes. There will be no more death or mourning or crying or pain, for the first order of things has passed away.' Rev 21:4. Until then, we live in a body and a world that is groaning and growing old. Sickness is part of this life - the 'first order of things'. But praise God that our Heavenly Father will always look after us in this life and we have a wonderful hope and promise for the life to come!
All the best.