You can think yourself sick to a certain extent, but you can't command a disease to strike you by thoughts of it. Nor can you cure yourself of a disease by thoughts, no matter how positive and happy and brave your thoughts are.
It may be possible to slow down ever so slightly the progression of the disease, though that is very doubtful too. What you absolutely can do by thinking positively as much as you can, is to make life a lot pleasanter for yourself and those around you.
If you are doing well without medicine, you just don't need the medicine yet. You will know when you need it - there will be no doubt in your mind at all when the time has come to get help.

I am a super positive optimist, but my PD progresses at its own speed.

birte