Warning: be wary when you read "MS treatment" in a news title. You need to look into
what exactly is treated. I'll explain this further below at [1].
There's a slowly progressing form of MS, and a quickly progressing form of MS. I'm not sure of the medical names in English.
You can definitely become old with MS.
My father got the diagnose in begin 70s (1972?) and I was born in 1983. He passed away in 2015 due to complications of MS. The disease affected him everywhere. I mean, I never seen him properly walk, but he only ended in a wheelchair end of '00s. It affected his short-term memory. It affected his kidneys, he was on dialysis for about 6 years. Eventually due to other complications he got infections, ended up with an amputation. He never fully recovered from that. He got infections elsewhere, and half a year later passed away.
[1] My father always kept hope for getting a treatment. He tried a lot of (insane) diets back in the 70s and 80s. None worked. Treatment-wise, they can stop the disease from progressing, but the people who get that treatment who are first in line are youth and people with the quickly progressing version. My father lacked both these variables, so he down below on the list.
Now, from what I understand in this century there's been various medication which can severely slow MS progression down, or even (more recently) completely halt the progression. The challenge with MS nowadays is reversing the damage done.
> But no matter what you decide, keep living.
We decided to stop with dialysis because QoL (Quality of Life) was near 0. My father's body was done. He's always fought the disease, till that point, and he had the mindset you described. He had to adapt to his new limitations all the time. I grew up with a father who was cursing a lot, but had a strong will (I suspect he had autism, like I have).
What I'd argue you need to realize is go carpe diem _without_ doing stupid "YOLO" stuff. If the progression of the disease cannot be stopped) your QoL is going down, and you don't know exactly how it is going down (you may have some ideas though, and you get monitored by doctors). You can use this to plan things you still want to do.
I also want to add that growing up with an ill father affected me in some negative ways, but there's also a clearly positive one. I have compassion for ill people, for weaker people, for minorities, etc. I believe it is because of growing up with an ill father, because the rest of my family on my father's side (cousins most notably) is [IMO] weak in this.