I think Ben offered good advice.

I would like to complement it with something I heard from professionals who treat people with health anxiety disordeds. Apparently the best strategy in many cases is not to tell people that they are fine, that their symptoms are self-imposed, that the activities they engage in are not dangerous, etc. We all know how difficult it is to reassure an anxious person with rational arguments.

Instead a common strategy is to insist on the opportunity cost of anxiety: how many opportunities do we miss out because of our anxiety? How many hours/days do we spend worrying (irrationally) instead of doing something meaningful with our time? How many relationships are we damaging because of our behavior?

It took me a good 3 years of PCS to incorporate these thoughts in my mental life and, while this is not a magic bullet, it helped me realize that the risk of isolation / depressing lifestyle / losing friendships etc. is sometimes much greater than the physical risks I was worried about.