I think that this whole process my be tougher on the caretaker than on the inflicted. I saw this with my parents, when my Dad was ill, and now again with my wife.
The problem has multiple aspects:
1) The inflicted party presumably knows precisely how he feels and what he is capable of doing. The caretaker sees the difference from day to day;
2) The inflicted party doesn't want to constantly think about Parkinson's Disease or whatever ailment affects him. The caretaker has no choice.
3) In many cases the caretaker knows more about the disease than the inflicted party.
Although, I write these almost daily, I don't think of myself as ill. I'm more careful in my day to day activities, but that doesn't mean that I will curtail them. I don't know what the correct answer is 1) Giving in to the challenges and discontinuing some activities that might prove problematical. or 2) Pushing the envelope, regardless of, what I consider to be, the slight chance of problem.
The answer is in a compromise.