I'm sorry to hear of your diagnosis Dekenba - I can relate, in small part, to what you're going through.
My father, who introduced me to scale modelling as a young nipper, has MS. He started experiencing symptoms in his early 40s and for a number of years he wasn't diagnosed (as you know, MS is one of those things where the nerve damage has to be big enough to show up on MRIs). He was a bit frightened for a number of years as to what was happening to him, as no one could tell him, until he got that diagnosis. Once he had that diagnosis, he had something defined that he could focus on, treat, and tackle, and that's the silver lining. You now have something that doctors can focus treatment in on. My father has been living with MS now for over 20 years, and through some good treatments, has slowed the progress to a virtual stand still (other things have gotten in the way of his treatment, but that's another story). Yes he can't run a marathon like he used to, but he can still do the things he loves to do.
I know that MS is a deeply personal battle, and it affects everyone differently, but don't give up hope - with some good treatment, and perhaps adopting to some of the larger scales, I'm sure you'll still be able to wield a hobby knife in anger.
Best wishes, don't give up!
Cheers,
Brad