At some point, 10 or 15 years ago, I got into the habit of saying goodbye to people by saying "stay well!"
I like it because it is cheerful, it closes a conversation without introducing a new topic, and it feels meaningful without being stilted (like "farewell") or rote (like "goodbye").
"Stay well" works nicely in a group of healthy people, but it is problematic with people who are ill.
Years ago, before "stay well!" was completely a habit, a colleague got prostate cancer. The treatment was long and brutal. I had to be careful when saying goodbye, but I didn't break the habit.
It is perhaps even worse with people who are chronically ill, because "stay well" (especially when I say it) has a casually privileged assumption that I am saying it to people who are already cheerfully well.
In the last week this phrase has got a new force for me. I really do mean "stay well" more than ever, but I wish I could express it without implying that you are already well or that it is your duty to be well.