How can I abort Mojave installation?
You already canceled it by quitting the installer, just delete the  installer if you do not ever want to upgrade, or keep it for a later install.

The /Applications/Install macOS Mojave.app can be double-clicked to restart the upgrade, whenever you want.



On a side note, if you do not want the App Store to do things automatically... then in System Preferences > App Store, uncheck the appropriate check boxes.

On my system I like to manually control when any upgrading occurs so I set my App Store preferences as in the image below.