I like mindfulness of thinking because I like thinking and because I want to find out the ways my thinking is leading me by the nose, so to speak.
I was interested this morning to notice three layers of thinking: first, the picutres and sounds that make up images, fantasies and so on; second, the sort of thought that says, 'Oh, there's not much going on there' or 'Theres a lot of distraction going on there' which is a sort of judging form of thinking, one step back from the images and sounds; third, there's the thought that says 'Oh, here I am observing my judging mind and the images and sounds my judging mind is judging: what a clever boy am I." That's the observing form of thinking, I guess.
Mindfulness of thinking can be endlessly fascinating - so long as I realise that the judgement that it's endlessly fascinating is thinking also!
