I felt like that before..
I say it's normal. It's all part of growing up.
Everything's going to be okay!
We got your back! <D
Parkinson's disease is a deficiency of the neurotransmitter dopamine. Dopamine is responsible for how the brain deals with stress, especially the fight-or-flight response. Thus, it affects greatly on the movements of the body. Also, dopamine is responsible for information processing. That is why people with Parkinson's disease have trouble in retaining their memories or be in deep concentration.
Numerous people.... Diabetics who are experiencing nerve degeneration of the extremities (something called Diabetic Neuropathy). Another group would be the elderly, who do loose sensation as age progresses. And lastly those with some sort of paralysis or peripheral nerve damage.