I'm sorry to hear it's been like this. And the confirmed diagnosis, most of all.

Were any of the doctors optimistic about at least treating symptoms? It may be incurable, but giving up is a bad mindset that will make you miserable. Any of the doctors not telling you to give up, may be one to take the advice of.

These things are all my reasons to keep living, so to lose those

Yeah, I sympathize. I am not sure how common it is to be faced with that kind of thing, but I think others experience it without the drastic medical source.

In a way, it's the perfect excuse to take a step back and re-evaluate your goals. This is not simple and it can be a huge pain to get advice about. I do strongly encourage you to attempt it (the re-evaluation of goals), because...well, what other option do you have? You do not want to be an invalid, you don't want people to treat you like one, which may mean them not feeling sorry for you, so you have to take some care not to fall deep into the pit of despair you may feel calling for you.

As an example of re-evaluated goals: I used to have the goal of being a video game dev. Eventually - after enough failure - I looked at it deeper and realized I actually had two goals hidden inside that one that were what mattered: the simple joy of co-operative effort with other people that share a desire rather than a responsibility, and the anxiety-soothing effect of finely tuning a series of systems to work well. I've actually gone a layer deeper on both of those since then, but I won't detail it here.

To the point, all humans need to have goals. Taking them away from a man can destroy him, but it's up to the man whether it does. I hope you can find a new set of goals moving forward, because it's hard to be happy without goals. I can't speculate on what may be beneath your lost goals, but you should give it some thought.