Trust is expecting something to happen; it is usually based on a promise made by another person and is the basis of all relationships in society. For example, I trust the person sitting next to me will not get up and stab me and I assume he trusts me in the same way. Trust is held in mutual balance until it is betrayed; if the person next to me takes out a knife I rapidly lose trust in him. Of course, trust is context dependent; if I am in a room full of murderers my threshold of trust is very high; enough to negate their potential actions (e.g. they are kept in handcuffs).
When Parkinson's enters your life, the disease sits next to you and brandishes a very big knife. Because a diagnosis is so unexpected you have nothing to equalize the relationship; you sit there defenseless. This disempowerment and unbalanced relationship shatters the trust you have in your ability to redress the balance; Parkinson's will acquire bigger and bigger weapons as time goes by and the feeling of exposure to its power will increase.
How can I handcuff Parkinson's and neutralize, as best I can, its possession of me? You can use the weapon of acceptance. Choosing to accept the situation you find yourself in, is to choose to look away from Parkinson's and see the rest of you. It is choosing to trust yourself to cope when it does attack.
Constantly looking at Parkinson's does not keep it in check; on the contrary, its threat is countered by living the rest of you...