Another welcome, Admac!
It's true that at first we are almost in denial, because the diagnosis is unexpected (and so distressing) that it feels unreal. At least, that's a common reaction, though not true for everybody.
Maddison is so right about the laughter! Happiness produces the most beneficial chemicals in the brain. Optimists do best in fighting these long-term illnesses. Actually, I don't even think of my case of PD as an illness any more. It's just a condition I live with, like being a bit too short and having rather weak lungs. Luckily, for most of us this is a slow-moving disease, and if you find the right medications for you and get lots of exercise, you can fight it effectively. After 18 years with PD, I am still living the same life as always. I know there are harder times ahead, but I try to focus on the present and keep my spirits up.
Best wishes to you.