Does prayer help?

My friends know by now that I am in hospital in Klagenfurt, recovering from a collapsed lung.
There may be an operation needed. Decision day: this afternoon or tomorrow.
In the meantime several of my friends have e-mailed, written and/or called, promising that they will pray for  my speedy recovery.

Of course I love them for this offer, since it shows that they care for me.

It does, however, raise the question of the usefulness  of "Prayer"!
If we consider that everything that happens, reflects the "Will of God" then, it seems to me, that prayer is useless or needless.
If, indeed, He wills that my friend shall NOT recover, then, our asking God that my friend should recover is useless. He is not likely to change his mind.
If, however, He has decided that my friend shall recover, my prayer is needless, since I am asking Him to do something, He has already decided to do. 
In either case, a prayer to influence the outcome of  a happening is either "useless" or "needless".

On top of all that, There is the question of His existence. .

Theists will say that He definitively exists, but they have no proof for this claim. All they have is a "Belief."
Atheists will claim that He does NOT exist, but they, too, have no proof for this claim. All they have is a "Belief."
So, I say, go on believing whatever you want to believe.

Bertstravels
will happily stay in his rational corner of the Agnostic