If you're using Mastodon, you can put your new posts under maximum privacy by doing both of these:
1. Log in through your server's website, go to Edit Profile > Require follow requests, save changes. This means only people you approve can follow you.
2. Set your posts' privacy to "Followers only" when you post them (the setting with the lock ๐ logo). You can make "followers only" default by going to Preferences > Other > Posting Privacy > Followers only.
However, only do this if you are okay with greatly restricting your audience by default. These settings will completely prevent non-followers seeing your new posts (unless you manually select a more public privacy setting when you write them).
Non-followers will not be able to search for followers-only posts, or see them in shares.
Also, bear in mind this privacy setting only applies to your new posts. If you've already posted something as public, that old post will remain public.