This is in my family too. One person always had a tendency of being overly worried and after children moved out and social life thinned or a bit, this became more prevalent.

After years of trying to push that person towards trying out new things and enriching their life, I kind of gave up. You simply cannot convince someone about a medicine if they don't feel there is a problem. Still it's hard to see believing the person could be enjoying life more, especially during their retirement.