Of course security comes with layers, and if you're not comfortable hosting services publically, use a VPN.

However, 3 simple rules go a long way:

1. Treat any machine or service on a local network as if they were publically accesible. That will prevent you from accidentally leaving the auth off, or leaving the weak/default passwords in place.

2. Install services in a way that they are easy to patch. For example, prefer phpmyadmin from debian repo instead of just copy pasting the latest official release in the www folder. If you absolutely need the latest release, try a container maintained by a reasonable adult. (No offense to the handful of kids I've known providing a solid code, knowledge and bugreports for the general public!)

3. Use unattended-upgrades, or an alternative auto update mechanism on rhel based distros, if you don't want to become a fulltime sysadmin. The increased security is absolutely worth the very occasional breakage.

4. You and your hardware are your worst enemies. There are tons of giudes on what a proper backup should look like, but don't let that discourage you. Some backup is always better than NO backup. Even if it's just a copy of critical files on an external usb drive. You can always go crazy later, and use snapshotting abilities of your filesystem (btrfs, zfs), build a separate backupserver, move it to a different physical location... sky really is the limit here.