Mindfulness. Being aware of one's own thoughts and feelings -- all of them. I find it to be a rather simple concept, fancied up sometimes in ways that make it seem exotic and foreign and accessible only to the special person. For me, it is surprisingly simple and easy to understand and connects to other theories of what causes mental disorders such as some of the writings of Freud. All that means there must be something to it!

Not necessarily easy to practice, though, since one has often been practicing just the opposite -- censoring one's thoughts -- most of one's life.