Just to throw some water on this fire before it grows, it's a total myth that we use 10% of our brains, started by phony psychics in the 1930's at traveling circus's. We use 100%, but as for how much we use at a single time, I don't know about that.

But yes, I agree that the brain can be trained to do remarkable things if you just gain the right experience, understanding, and discipline. For instance today I was at work, in a dark cold part of the construction site at 7:00 am and feeling pretty miserable. So after a couple hours I remembered some of my mental training (particularily in meditation), closed my eyes, and from having countless hours of meditative practice managed to put my mind in the peacefull, happy, and clear state within seconds. that state used to take me 20 minutes of intense meditation to maybe achieve.
I've been learning a lot more lately how the mind can be controlled and the different types of consciousness a person can willingly achieve. One of the most usefull skills I've only recently been developing is the ability to transferre extra oxygen and endorphines to areas in my muscles that are particularily painfull. I try not to do the endorphines too much though, don't want to burn something out (excessive seratonin can burn our your seratonin receptors and make you depressed, and I suspect most chemicals work that way).