From what you say it's genetics. I have to be honest with you that I was very active until I got peripheral neuropathy together with other ailments and it's made me feel negative. Presently though I am on a high which I haven't had in two years I have had manic depression for many years which has worsened as I've got older. I also have a partner with serious health issues he is 84. He is a very positive person fortunately. You are right about having a positive attitude and a surely wish I could be the same but the manic depression coupled with the health issues is probably what is the danger for me. I am retired was a PA to director of our local hospital. Used to swim a mile at the pool three times a week and walk there and back. I did a lot of other things but having peripheral neuropathy has been the the biggest thing. Manic Depression is absolutely awful to but the medications are all rubbish so I'm unmedicated but see a doctor for it as I do neurologist. You surely will be like your Dad. I hope my partner survives to that. He isn't that active though due to his condition. COPD and heart failure amongst other things. When I read your article you just sounded as if you were all okay. Well you aren't now I know but you won't be beaten. That's great but genetics I would say comes into play.