I'm not GP but I'll make a suggestion I have already on a different, although somewhat related thread.
Anything in the warrior literature will help you find yourself, your limitations and help unlock your potential.
Way of the Peaceful Warrior, by Dan Millmann, is a very good introduction to the whole subject. It's fairly easy to read but absolutely full of little gems of wisdom if you're willing to see them. Once you get that, look for the heavier stuff.