I believe in GOD words...that say "nothing is impossible for GOD" but this student leaved me very worry.
Well if god were the one learning to play the piano there probably wouldn't be too much to worry about then.
I think as humans we all have limitations. What is it that you are worried about being impossible? Learning a particular piece? Becoming the world's greatest piano virtuoso? Etc?
I'm just starting to learn the piano at 57. I have mental disabilities now that drastically interfere with my learning process. That doesn't mean that I'm going to give up learning to play. But it most likely means that my learning curve will be a lot slower than it otherwise might be and I may even run into limitations of what I can actually play. That doesn't worry me. Even perfectly healthy people run into limitations. After all, every pianists who starts out in earnest to play the piano does not become a great virtuoso. I've talked with perfectly healthy pianists who know they are never going to become great and accept the confines of their abilities. Not that they don't try to improve, but they just don't have unrealistic expectations.
The real factors in how good of a piano player you will become probably have much more to do with how much time you have to practice, how sincerely interested you are in becoming good, and perhaps even how much you get into the music.
The best saying I know is, "You never know until you try". That's really all you can do. No one here can say whether or not you might become a great pianist. It's not my dream or intention to become a great pianist so I'm not worried about. I just play for my own enjoyment and that's good enough for me.
After all God is watching me play so I already have a great audience.

You say you play at your church and you do well. Just keep playing what you do well and you'll be alright. If you run into pieces that you find too difficult it's up to you whether you want to tackle them as a challenge, or just by-pass them as being not all that important. After all, there's really no reason that a pianist should be able to play just anything. I personally feel that it's better to know a limited repertoire of pieces that I can play really well, than to try to play a lot of things that I don’t play so well.
How you proceed is your own choice. And freedom of choice is one of the greatest gifts that god has given us.

I might add too that if you find a passage or phrase that is giving you extreme problems don't be afraid to modify it a bit by dropping a few notes or playing it slightly different than tradition has it. If you play the rest of the piece very well most people probably won't even notice that you've simplified a few parts here and there. After all, you're a musician not a robot. View things from an artistic point of view rather than a purely technical point of view and just enjoy the music.