My advice would be to ALWAYS set the levels so that you can hear yourself, and use a tone that you can differentiate from the recording. When you can hear yourself it builds up different parts of the nervous system (like the speech/language part of the brain), instead of just hand-eye coordination and reflex. DISCLAIMER: I'm not a neurologist, it's just stuff I read that correlates well with my experience.
What I do is I use a custom tone that cuts well through most mixes, so I can hear myself 90% of the time without fiddling with the settings. ymmv