On Meditation...

The founder of our Order, Rev. Master Jiyu-Kennett, who studied meditation under some of the greatest meditation masters of Japan, translated the classic Zen texts on the mind of meditation as saying that the critical element is, "Do not try to think, and do not try not to think". She likened the mind of meditation to a person sitting under a bridge beneath a busy road. The "traffic" on the road is our thoughts, feelings, perceptions, emotions, etc. To try to mentally stop the traffic is to "try not to think". The same is true of dulling the mind to the point where no traffic is noticed at all. These approaches would seriously unbalance the harmony of meditation: the first one by increasing concentration to the point of excluding awareness, the second by decreasing awareness to the point that only concentration is left. On the other hand, to leave one's sitting place, get up and accept a ride in one of the cars is to "try to think". One's mind is literally "captured" and "carried away" by a particular thought or feeling, so that what was simply a passing thought turns into a ten minute chain of thinking. Here, the concentration has been insufficient, and awareness has lost touch entirely with the basic fact of things-as-they-are: the fact that we are just sitting there. Whenever we find that we are doing something other than just sit there, we gently bring our mind back. This is done over and over again, and is the work of meditation practice.

 Another useful observation which Rev. Master Jiyu-Kennett made about meditation was the distinction between natural and deliberate thought. Suppose, for instance, that a dog barks while we are meditating. We naturally hear the sound, and perhaps the thought occurs to us that a dog is barking. These are examples of natural thought; they are part of things-as-they-are, part of simple, aware sitting. This is meditation, and nothing needs to be done about it. But suppose that we continue the chain of thought: we next think that the barking disturbs our meditation, that our neighbor should control their dog better, that something really should be done about this lack of consideration·, and the next thing we are aware of is that we "wake up", realizing that we have spent the last five minutes giving our neighbor a lecture. This is deliberate thought and is inconsistent with serene reflection meditation. We need to bring our mind back to the awareness of simply sitting there. 

http://www.berkeleybuddhistpriory.org/pages/meditation/meditation.html