Managing access to pages

Hello!
I setup a test system and play around with Grav. My intention is to create something like a personal Notebook, because I like the file based content storage.
My question is how to manage access control to pages. Some pages should be accessible to non users, other should only be visible and accessible to me, or better to the usergroup internal.
I played with page groups but for my understanding there is a option missing where I can disable access to non logged in users. Or I am completly wrong. I couldnt find any mathing article in the docs, so maybe someone can help me 🙂