Hi Olly, no worries. You’re not the first do do it! It’s caught me out a couple of times…
Phones is effectively the PAFL output and LR is sent to PAFL by default, so if you pull the Main LR fader down, you lose the LR in your cans (phones) too.
In the studio I use the Alt out for monitors with this assigned to LR Pre in Setup > I/O Patch > Surface.
This way I can leave the LR Main fader and use the independent Alt Out level control to turn down my monitors.
Alternatively, you can connect a separate headphone amp to a stereo mix out and use this to give the artist their very own independent headphone mix. This way they can even have FX on their mix without you having to hear it in the main LR mix. Very useful for divas… and frees up the phones for you too 😉
Let me know if you need any more info.
Cheers. Harry.