Take a couple of days off a week, every week in my opinion. Grinding 10+ a day, every day, will wind you down, no matter how much you love the game.
I'd suggest taking up an alternate hobby to help fill the free time as well. Now that I have a daughter, spending more time with her works for me.
Before that, I would spend time catching up on current events by reading through Google News, as well as some alternative news sources, getting out to spend time with friends, or getting some decent novels or history books that aren't poker related to help me relax.
Always take at least 1 day a week where you don't do anything poker related to help relieve a little of the stress from the daily grind.