The application of mindfulness has to be precise. If we cling to our practice, we create stagnation. Therefore, in our application of the techniques of mindfulness, we must be aware of the fundamental tendency to cling, to survive. We come to this in the mindfulness of life, or survival. We encounter this tendency in the form of clinging to the meditative state. We experience the meditative state and it is momentarily tangible, but in that same moment it is also dissolving. Going along with this process means developing a sense of letting go of awareness as well as of contacting it. This could be described as touch-and-go: you are there—present, mindful—and then you let go.
From "The Four Foundations of Mindfulness," in The Sanity We Are Born With: A Buddhist Approach to Psychology, pages 27 to 28.