I prefer What Every Musician Needs To Know About The Body. Here's something I posted some time ago (http://www.pianoworld.com/forum/Post1302635)

Hello,
I think the piano is probably what saved you. Otherwise you wouldn't be questioning and trying to fix your tension.

I grew up in a very tense environment and as a result of that I held my muscles very tightly. This caused me a lot of pain. I have done a number of things that have helped. 1. myofascial release. 2.yoga and qi gong 3. I did a lot of "mind" work and would read all kinds of books by people like Wayne Dyer, The Dalai Lama, Deepak or anything that presented itself to me. Also, there is a book called the feeling good handbook. It's really interesting because it explain all the types of thoughts that we have. Because sometimes we don't even realize how our thoughts are making up feel and effect us physically.

Finally, I am reading this book called Effortless Mastery by Kenny Werner. Its a great book. I think you will enjoy it.

The piano can be your guide to making you aware of the progress you are making. Playing used to be uncomfortable for me. So I had to kind of go back and forth. But now I actually feel better after I play.

Good luck

I can relate to your problem. I'd found that really thinking before playing a note really helps. I also find that when I notice tension I need to relax straight away. Also, there are teachers who specilize in helping with tension. Google the alexander technique for more information.

I sometimes can't play at all because of stress or tiredness but what works for me is to work on a piece or exercise or scale or whatever for intervals of 30 mins and rest of 5mins. I literally get up, stretch, drink something, do a yoga position, etc...

maybe it works for somebody else too.