To meditate upon thoughts is simply to be aware, as thoughts arise, that the mind is thinking, without getting involved in the content. —Joseph Goldstein
When you are practicing Zazen meditation do not try to stop your thinking. Let it stop by itself.
If something comes into your mind, let it come in and let it go out. It will not stay long.
When you try to stop your thinking, it means you are bothered by it. Do not be bothered by anything.
It appears that the something comes from outside your mind, but actually it is only the waves of your mind and if you are not bothered by the waves, gradually they will become calmer and calmer.…
Many sensations come, many thoughts or images arise but they are just waves from your own mind. Nothing comes from outside your mind.…
If you leave your mind as it is, it will become calm. This mind is called “big mind.”
Just let things happen as they do. Let all images and thoughts and sensations arise and pass away without being bothered, without reacting, without judging, without clinging, without identifying with them.
Become one with the big mind, observing carefully, microscopically, all the waves coming and going.
This attitude will quickly bring about a state of balance and calm.
Don’t let the mind get out of focus. Keep the mind sharply aware, moment to moment, of what is happening, whether the in-out breath, sensations, or thoughts.
In each instant be focused on the object with a balanced and relaxed mind.
—Suzuki Roshi in Zen Mind, Beginner’s Mind