My DH has Parkinsons - we believe that it started before the age of 60. He knew what he had long before he chose to alert the medics to this - he is himself a doctor, so knew straight away what it was. He has been on treatment now for about 8 years.
The saying with PD is that you "die with it but not of it."
It has made a huge difference to our lives, particularly in wiping out most of our fun plans for our retirement. Over the years he has deteriorated and the number and range of drugs that he needs has increased. I spend most of my day saying "Have you taken your tablets?"
People do not realise that there is a lot more to PD than the tremors: loss of taste and smell, general weakness, hypotension (leading to sudden collapses), slowed down gut (severe constipation), depression and anxiety, difficulty in swallowing, weak voice - I could go on!
Some of the drugs carry their own problems: obsessional behaviours (sex, gambling etc.), blocked nose, nausea, sleepiness, acting out dreams (he once attacked me in his sleep!) etc.
But we just bash on - adapting to each change as it comes along. I would not recommend PD as a life choice, but, as with everything, you just take what life throws at you and get on with it, concentrating on what CAN be done and not on what can't.