Hi MC,
Health in the studio:
Ears. When they go, so does your recording ability.
No "I will record this tune/these tunes today AND mix them down afterwards". Your ears will gradually get more and more deaf as the day goes, and you will keep turning up the volume to compensate.
Golden Rules:
Recording sessions done at a SENSIBLE volume, for a SENSIBLE length of time.
Sleep.Then:
Mixing at SENSIBLE volume, with a few loud playbacks for perspective. Also a few really soft ones, for same effect.
Get up, move around; stretch regularly, both when up and when at recorder; you'd be amazed at the crackling as your bones loosen up.
Stay hydrated, lots of water thoroughout the day.
Daylight is good, sunlight gives you Vitamin D.
Tension never created anything good. If it doesn't work, go for a walk or do something else entirely for a while. If it doesn't flow at least somewhat, you are in your own way, creatively speaking.
And don't get frustrated by the fact that it might not be working for you right then, because you are in the company of thousands at that very moment
Best,
CC