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.

You can’t make someone change, if they don’t want to.

This can be very sad. The person you love just fades away.