I totally agree. For the past few years, my life (as a teacher) has been a sustained run of work, pressure, and more work, with barely enough time to sleep or eat. My well-being has suffered, and I find myself in a daze a lot of the time. I feel this has prepared me for the rigor of graduate school, but also, I hope very much there will be lifestyle changes.
When I had a vacation a short while ago, I started feeling human again for just a short while - actually enjoying some activities I used to enjoy, like reading and writing, and not having a headache 99% of the time. It was like finally getting rid of a long, stifling hangover. I imagine graduate school can be like that too, if you let it. Work is important, but so is living life. And balance probably makes you more mentally apt, anyway.
To quote Barbara Bush paraphrasing Ferris Bueller, "Find the joy in life, because as Ferris Bueller said on his day off, 'Life moves pretty fast; if you don't stop and look around once in a while, you're gonna miss it.'"