Think of it as having a different role in society. We cannot be something other than we are, but our role is great, too. Definitely follow your instinct that you truly want to change work directions; that is what I would do. The good news is that it is easier than ever to stay mentally active because of the internet, so start there and figure out what you want to do next. That is a great thing about increased human longevity. You can do many things in one lifetime.