In all honesty, just need to find other games to pass time by when you "finish" the content you enjoy. I think quitting is an extreme, and just either taking a break or even keeping the sub going and play other games until you feel an itch to do a DF run (it does happen lol). I personally have a space sim game and various offline games I use when I'm not into XIV at the time. Usually within a few days I'll get the urge to come back and do something even if only for an hour.

Edit: Also, can try rolling an alt on a vastly different server. In example, one of the JP servers, while communicating will be a bit harder with auto-trans, its interesting seeing the playstyle differences.