Bhante Henepola Gunaratana in Chapter 7 ("What to Do with Your Mind") of Mindfulness in Plain English discusses the meta-concept of observing one's thoughts rather than just thinking them:

There is a difference between being aware of a thought and thinking a thought. That difference is very subtle. It is primarily a matter of feeling or texture. A thought you are simply aware of with bare attention feels light in texture; there is a sense of distance between that thought and the awareness viewing it. It arises lightly like a bubble, and it passes away without necessarily giving rise to the next thought in that chain. Normal conscious thought is much heavier in texture. It is ponderous, commanding, and compulsive. It sucks you in and grabs control of consciousness. By its very nature it is obsessional, and it leads straight to the next thought in the chain, apparently with no gap between them.

... The difference between being aware of the thought and thinking the thought is very real. But it is extremely subtle and difficult to see. Concentration is one of the tools needed to be able to see this difference.

Deep concentration has the effect of slowing down the thought process and speeding up the awareness viewing it. The result is the enhanced ability to examine the thought process. Concentration is our microscope for viewing subtle internal states. We use the focus of attention to achieve one-pointedness of mind with calm and constantly applied attention. Without a fixed reference point you get lost, overcome by the ceaseless waves of change flowing round and round within the mind.

We use breath as our focus. It serves as that vital reference point from which the mind wanders and is drawn back. Distraction cannot be seen as distraction unless there is some central focus to be distracted from. That is the frame of reference against which we can view the incessant changes and interruptions that go on all the time as a part of normal thinking.

And then, as the Zen advice says, "You know the space between your thoughts? Make it larger!"

(cf. Unselfing (2009-01-14), The Watcher (2010-11-15), Let the Mind Pass By (2010-12-28), Turning Attention Inward (2011-04-17), Coming Back to Your Breath (2011-09-25), Power of Now (2011-12-14), Pay Attention (2013-12-05), Watch the Wound (2015-07-24), ...) - ^z - 2016-04-01