Mindfulness involves meta-cognition. What is meta-cognition?

As Bishop et al. (2004) note, mindfulness involves self-regulation of attention and meta-cognition, in other words, sustaining attention and thinking about one's thinking. Harris (2008, p. 40) shows us how we can go from having a thought that I am X to I'm having a thought that I am X to I notice that I am having a thought that I am X. Sometimes these thoughts are stressful or disturbing. Going from I am incompetent to I'm having a thought that I am incompetent to I notice that I am having a thought that I am incompetent goes from a simple stressful cognition to a more complex and less stressful meta-cognition.