Nvidia Arch user here, are you just forgetting to rebuild your kernel modules after a kernel or nvidia driver update?
You can just add a pacman hook that triggers mkinitcpio -P after the linux or nvidia packages are updated. I've never had a no-GUI situation from a stray update... maybe one or two that were my own doing when trying to set up UKI's though.
What did you edited ? Arch user here, never had this kind of issue. Also if you managed to install Arch, you should be able to fix it(maybe you switched from terminals, try ctrl+alt+1-9)
As long as I can get into the terminal I can fix the GUI. What really sucks is when it something that runs in the DM init sequence was using Python but a Python upgrade changed the import path and no it keeps restarting and I need to boot from a USB to disable that service so I can log into something and properly fix it.