Cammarak, I just have to say - have an accident and injure or kill someone else, if you haven't declared your diagnosis then you won't be insured and your family could lose everything anyway and you will have the guilt on top ... If you feel it is too dangerous to drive on ice, then how do you think you would be able to react if there was suddenly an urgent situation on the road in front of you without ice? I know, truly, it's a terribly hard thing to give up. If you had to stop driving is there no way someone else could get you to work and back? just sayin
On the other note. We say emphatically to people on DIHALS section that symptoms do not come and go or get better. That isn't exactly how it is, and yet it is.
I will try to explain. If you think of how you are on your very best day, then yes you may fatigue yourself, or it may be extra cold or some other influence and the next day you may be far worse. After a day or 2, you may 'get better', returning to how you had been on your previous best day, maybe nearly returning to there. BUT, you won't go to even better than you had been on that best day, let alone suddenly have all your strength back.
It's too hard a fine point to make to those who are in anxiety, but it is true. Just like me who does not have ALS/PLS, I have some days I have better energy and can do more for longer. Some days you will be worse, but the next a little better. The big thing is you won't 'get better' and you will decline (sorry I hate saying this stuff). So a month or year later, your very best days will be at a decline from your very best day in the past, and your worst days will be worse again still.
In the winter, Chris would find that of a morning when it was most cold, he may not be able to do anything at all with his hands. A few hours later, they had improved a lot and he could hold a cup again. By the summer, even on his good days he couldn't hold a cup, ever. So even though his strength went up and down a bit when he had use of his hands, they still continued to decline. Being rapid ALS what Chris experienced was all much faster than you should have, but the analogy is still the same, he just had it happening in a short time frame.