If you don't want the overhead of another extension, a quick win is to add this to your `/etc/hosts`:

    127.0.0.1	facebook.com
    127.0.0.1	www.facebook.com

After a week you'll completely forget you have facebook.

BTW, there is a github repo that lists every domain owned by facebook, they have ~900 domains now.

https://github.com/jmdugan/blocklists/blob/master/corporatio...

Yes, I mentioned this one in my comment ("editing the host file with ES File Explorer"), but it requires your phone to be rooted.